The definition for OSVs was originally conceived for vessels that transport supplies and offshore workers to offshore facilities engaged in oil and gas exploration, exploitation, and production. Over time and in response to the needs of the oil and gas industry, OSVs have become more involved in an increasingly wide range of support services beyond the traditional transportation of goods and people. Nevertheless, when inspected under 46 CFR Subchapter L, operations are limited to those in which the vessel "regularly carries goods, supplies and individuals in addition to the crew, or equipment in support of exploration, exploitation, or production of offshore mineral or energy resources."¹ If a vessel engages in support activities that are beyond the scope of this definition then the vessel must be authorized to conduct the activity under a different type of endorsement (such as 46 CFR Subchapter I, D, or M).

¹ See 46 U.S.C. § 2101(25), this definition is mirrored in Coast Guard regulation 46 CFR 125.160.

Published 24May2019; updated references 05Jul2022.

Yes. As per the General Definitions of 46 U.S.C. § 2101, an "Offshore Supply Vessel" is defined as a "motor vessel that regularly carries goods, supplies, individuals in addition to the crew, or equipment in support of exploration, exploitation, or production of offshore mineral or energy resources."

"Energy resources" does include wind energy. Therefore, self-propelled vessels that support wind energy do meet the definition of an OSV as defined in 46 U.S.C. § 2101(25), because they comply with the three statutory requirements:
   1) they are motor vessels;
   2) they carry goods, supplies, individuals in addition to the crew, and/or equipment; and
   3) they support the exploration, exploitation, or production of energy resources.

Published 08Apr2019.

Any vessel engaged in an OCS activity is subject to inspection in accordance with 33 CFR Subchapter N, Part 140, Subpart B.

An "OCS activity means any offshore activity associated with exploration for, or development or production of, the minerals of the Outer Continental Shelf" as defined in 33 CFR 140.10. The definition is broad and includes a whole host of activities beyond drilling and production type activities (e.g. seismic survey, construction, subsea construction, and well intervention, to name just a few). The key is that the activity must be related to exploration or the ultimate production of mineral resources on the OCS. Note: Energy resources beyond minerals (e.g. wind) are not included in the definition of an OCS activity regulated under Subchapter N, but are included in the in the definition of an Offshore Supply Vessel that is U.S. Flagged and regulated under 46 CFR Subchapter I or L (see definitions at 46 CFR 90.10-40 and §125.160, respectively).

A "Unit means any OCS facility, vessel, rig, platform, or other vehicle or structure, domestic or foreign" per 33 CFR 140.10.

The inspection requirements for "vessels" (also defined in 33 CFR 140.10) engaged in OCS activities are listed at 33 CFR 140.101(a) and (c) through (e). §140.101(c) provides for announced and unannounced inspections that may be directed by the Officer in Charge, Marine Inspection (OCMI) to determine if units engaged in OCS activities are in compliance with the applicable requirements of Subchapter N. §140.101(d) lists what may comprise the inspection and §140.101(e) stipulates the recognition of valid international certificates issued to foreign units for matters covered by the certificates, unless there are clear grounds to believe that the unit or its equipment do not meet the particulars of the certificate.

U.S. flagged vessels (other than MODUs) have not typically been inspected under the provisions of 33 CFR Subchapter N due to the routine inspections of those vessels under the Subchapter(s) of 46 CFR that apply to the particular vessel (i.e.46 CFR Subchapters I, L and T), with the exception of 33 CFR Part 143, Subpart E for "standby vessels" (also defined in 33 CFR 140.10).

Foreign flagged vessels (other than MODUs and production units) have also not typically been involved in direct inspections offshore, although the provisions of 33 CFR 140.101(e) can be applied.

The parts of 33 CFR that apply to vessels engaged in an OCS activity (other than MODUs or production units/facilities) are as follows:
   • Part 140 - General (overarching requirements and procedures)
   • Part 141 - Personnel (citizenship requirements and exemptions)
   • Part 142 - Workplace Safety and Health
   • Part 143 - Design and Equipment, Subpart D (all vessels) and Subpart E (U.S. Flagged standby vessels)
   • Part 146 - Operations, Subpart D (casualty notifications) and Subpart E (notice of arrival)

Published 23Apr2019.

Yes, as long as the goods, supplies and/or equipment;
   1) do not hinder the vessel’s ability to render assistance to the facility that the vessel is designated to assist; and,
   2) are not hazardous material.

Reference: 33CFR 143, Subpart E provides the requirements for standby vessels.  In particular to this FAQ, 46 CFR 143.401(d) & (e), as included below, state the requirements regarding cargo carriage.

§143.401 Vessel certification and operation.
Standby vessels must meet the following:
  (d) Not carry or store goods, supplies, and equipment on the deck of the standby vessel or in other locations that may hinder the vessel’s ability to render assistance to the facility that the vessel is designated to assist.
  (e) Not carry or store any hazardous material.

Published 03May2019.

An OSV that performs towing is required to be operated by an officer holding master or mate of towing vessels, or a master or mate of self-propelled vessels greater than 200 GRT who also hold a completed Towing Officer Assessment Record (TOAR). This requirement applies to all officers standing watch. This is consistent with 46 U.S.C. § 8904 and the regulations found at 46 CFR 15.805(a)(5), 46 CFR 15.810(d) or 46 CFR 15.535.

Published 24May2019.

Yes. Per 46 U.S.C. § 8701 and Marine Safety Manual (MSM), Volume III, on vessels that are at or over 100 GRT¹, a person engaged or employed onboard a vessel must have a MMC². The Coast Guard has interpreted³ this to mean that any person working on board in support of the vessel's mission must be credentialed. Divers and dive-support personnel employed on a vessel that is contracted to provide dive support services are required to be credentialed. The Subchapter under which the vessel is certificated does not affect the MMC requirement.

Whether an individual is "part of the crew" or a person "in addition to the crew" is immaterial to the MMC requirement. The MMC requirement is controlled by 46 U.S.C. § 8701(b), which states:

"A person may not engage or employ an individual, and an individual may not serve, on board a vessel to which this section applies if the individual does not have a merchant mariner's document issued to the individual under section 7302 of this title. Except for an individual required to be licensed or registered under this part, the document must authorize service in the capacity for which the holder of the document is engaged or employed."

This statutory requirement is included in MSM Vol. III, Chapter B4, Manning Requirements For Credentialed Ratings and Non-Credentialed Crew, C(1) (pp B4-5, B4-6), states:

Merchant Mariner Credential/Document Requirement. (2014, 2017): Under 46 CFR 15.403, every person below the grades of officer and staff officer employed on any U.S. flag merchant vessel of 100 GRT or more, except those navigating rivers exclusively and the smaller inland lakes, must possess a valid merchant mariner credential (MMC) or merchant mariner's document (MMD) with all appropriate endorsements for the positions served. For technical or industrial positions for which the Coast Guard does not require a particular credential, the seaman must possess an MMC endorsed for entry ratings. [emphasis added]

Whether the charterer or ship owner hires an individual is immaterial to the MMC requirement. That the charterer pays the salary of a particular person or decides what type of work is being done by that person does not dictate who is required to have a MMC. The requirement to hold a MMC is driven by the plain language of the statute that requires an individual employed upon a vessel to hold the document. As such, ROV operators, divers, anchor handlers, and other Industrial Personnel engaged or employed in the furtherance of the ship’s mission require a MMC unless expressly excluded by 46 U.S.C. § 8701.

¹ 46 U.S.C. § 8701(a) applies the MMC requirement to merchant vessels of at least 100 gross tons with several exceptions. These exceptions do not include OSVs operating on the U.S. OCS.
² 46 U.S.C. § 8701(b). Note that the MMC combines the elements of a traditional license and Merchant Mariner’s Document (MMD). See 46 CFR 10.107. The requirements to hold a license or MMD equally apply to the corresponding MMC.
³ Marine Safety Manual, COMDTINST M16000.8B Change 2 (July 5, 2017),Vol. III, Ch. 1, General Provisions for Vessel Manning, Sec. H(1), pg B1-9. See also MSM Vol III, Ch. 4, Manning Requirements for Credentialed Ratings and Non-Credentialed Crew, Sec. C(1), pg B4-5.

Published 28May2019.

Yes. Industrial personnel are not considered when establishing or fulfilling minimum safe manning levels required for the vessel. As such, these personnel are not counted for the purposes of applying 46 U.S.C. § 8702 which should only be calculated using the required persons onboard as stated on the Certificate of Inspection (COI; CG-841).

Published 28May2019.

No. The definition of offshore worker as defined in 46 CFR 125.160 "means an individual carried aboard an OSV and employed in a phase of exploration, exploitation or production of offshore mineral or energy resources served by the vessel; but it does not included the master or a member of the crew engaged in the business of the vessel, who has contributed no consideration for carriage aboard and is paid for services aboard."

Offshore workers are those typically aboard the vessel solely to be transported to an offshore facility. They are in effect a type of passenger, but one that is statutorily exempt from the passenger definition (46 U.S.C. § 2101(29)(B)(iv)) and the vessels that carry them (OSVs) are thus exempt from the requirements associated with passenger vessels. They are referred to as "individuals in addition to crew" in the OSV definition at 46 U.S.C. § 2101(25). In general, they should not be working aboard the vessel, and as such would not be required to hold a MMC. Nonetheless, if they are employed to work aboard the vessel (regardless of who pays their salary), they must have a MMC. As such, a dive team which is employed to conduct dive operations in support of exploration, exploitation, or production of offshore mineral or energy resources from an OSV would be required to hold a MMC.

Published 28May2019; updated references 05Jul2022.

A portable accommodation module (PAM) is considered any non-integral, enclosed space installed on a host vessel or facility and occupied by personnel for berthing, recreational, service, or industrial purposes. Examples include sleeping cabins, offices, hospitals, recreational spaces, dining spaces, lavatories, galleys, laundries, laboratories, workshops, wireline units, mudlogger rooms, ROV control rooms, dive control rooms, and any other similar spaces¹. The cognizant OCMI is responsible for making determinations on whether or not a module is considered a PAM.

¹ CG-ENG Policy Letter 01-16, Portable Accommodation Module Guidance, is the reference for this FAQ and contains detailed information to guide industry, authorized classification societies, and CG inspectors through the process, ranging from design and construction of the module to approval and installation.

Published 23Oct2020.

Short Answer: The cognizant OCMI approves PAM installations, but only after certain considerations have been satisfied per CG-ENG Policy Letter 01-16, Portable Accommodation Module Guidance. Some of these considerations are best satisfied prior to, and during, the PAM construction and before the host vessel is even selected. PAMs that address these concerns during construction may affix data placards indicating Coast Guard approval.

Discussion: The PAM approval process, in total, begins with the approval of the module itself.

Shipping regulations make no provision for installations onboard vessels that are temporary. It is crucial to understand that installing a PAM, no matter the PAM size, is a vessel modification and must comply with the same requirements as a permanent modification to the vessel (plan approval, construction oversight, inspection, etc.). Policy Letter 01-16 provides a means for builders and operators of PAMs to streamline the inspection process by separating the pre-installation plan review from the installation plan review.

Modules approved under Policy Letter 01-16 are constructed using the American Bureau of Shipping (ABS) Guide for Portable Accommodations Modules (May 2014) or, if approved by the Marine Safety Center (MSC), an equivalent, alternative standard. Each approved module has a unique data plate and corresponding MISLE (Marine Information for Safety and Law Enforcement) activity attesting to its construction oversight. See Policy Letter 01-16 Enclosure 3 for detailed guidance on the construction process and standards.

Once the module has been approved and certified for use on a vessel, and before installation, the operator must submit an application for inspection to the cognizant OCMI stating the purpose, general arrangement, and intended period for which the module will be on board. Additionally, the OCMI shall ensure the engineering plans detailing the host vessel's installation have been submitted to MSC. Engineering plans, distinctly separate from module construction plans, include, but are not limited to, items such as damage stability and installation location and must have MSC approval before installation.

To remove a PAM, the operator must submit an application for inspection to the cognizant OCMI, stating the vessel's removal of the PAM and intention to return to "pre" PAM configuration. See Policy Letter 01-16 paragraph 5.c.vi for additional considerations.

It is incumbent upon OCMIs to engage with the installation and removal of PAMs, regardless of how "routine" it may seem to the operator or inspector.

NOTE: This FAQ is premised on a non-Alternate Compliance Program, traditionally-inspected vessel. Vessel classification status for a traditionally-inspected vessel does not alter the PAM approval process. Additionally, this FAQ addresses "new" and not "existing" PAMs. See Policy Letter 01-16 Enclosure 3 for guidance on existing PAMs.

Published 23Oct2020.

No, they are not equal. OCS activities fall under 33 CFR Subchapter N. Both 46 CFR Subchapters I and L have provisions and standards for vessels to conduct dive operations, depending on the vessel’s service. Vessels inspected under 46 CFR Subchapter L (OSV) may act as a dive support vessel for activities that specifically support exploration, exploitation, or production of offshore mineral or energy resources. A vessel inspected under 46 CFR Subchapter I may act as a dive support vessel for activities that support exploration, exploitation, or production of offshore mineral or energy resources AND other industrial activities such as cable laying or construction.

Published 28May2019.

Yes. Any vessel operating as a multi-certificated vessel is required to have the type of service entered into the vessel's logbook or record. The Master of the vessel is required to identify which service the vessel is engaged in, dependent upon the operation being conducted in accordance with the definitions for the vessels service (46 U.S.C. § 2101, 46 CFR Subchapter L, or 46 CFR Subchapter I).

Published 28May2019.

No. A vessel is inspected under a particular Subchapter based on the vessel’s service. A vessel that changes service would be subject to inspection under the applicable Subchapter, no matter the brevity or rarity of the work, unless a particular regulation allows for it. For an OSV to engage in dive operations for non-OCS energy related functions, the vessel must be multi-certificated.

Pub. L. 96-378, enacted on October 6, 1980, made changes to how conventional OSVs were to be inspected by the Coast Guard. In 1983, the provisions of Pub. L. 96-378 were consolidated, and re-codified in Title 46. Prior to recodification, the House Committee commented on how it interpreted the definition of an OSV. The House Committee report, H.R. REP. 98-338, (1983), stated:

"Section 2101(19) defines offshore supply vessel as a class of vessel that is limited by tonnage and its employment in the mineral and oil industry and while so employed it is not a small passenger vessel." [emphasis added]

The phrase “limited by… its employment in the mineral and oil industry” leads the Coast Guard to conclude that Congress’ intent was to limit the ability of a vessel to receive an endorsement as an OSV to vessels that "regularly" operate in the service of energy exploration.

An OSV may conduct operations outside of their Subchapter L COI, but would be required to become multi-certificated for those operations. This position is supported by the same House Committee report which states:

"It should also be noted that a particular vessel can, when engaged in various types of operations, be subject to varying inspection laws. For example, an offshore supply vessel could be classed as a small passenger vessel or a passenger vessel when it operates as a crew boat carrying individuals other than those defined in section 2101(21)."

This shows that the House anticipated that a vessel may conduct different operations and provides flexibility to regulate that same vessel under different Subchapters depending on the operation the vessel is conducting.

Published 28May2019.

No. Vessels inspected under 46 CFR Subchapters T or K may engage in recreational diving, if so endorsed on the Certificate of Inspection (COI; CG-841). Vessels supporting exploration, exploitation, or production of offshore mineral or energy resources, who are engaged in commercial diving, are required to be certificated under 46 CFR Subchapters I or L.

Published 28May2019.

No. Vessels inspected under 46 CFR Subchapter I may engage in lightering support. Vessels certificated under 46 CFR Subchapter L may only engage in lightering support if the tanker received the oil from an offshore unit engaged in exploration, exploitation, or production of offshore mineral or energy resources on the U.S. OCS (e.g. MODU, FPSO, etc.) AND the oil or mineral never reached shore prior to lightering operations. This is consistent with the definition of "production" contained in 43 U.S.C. § 1331(m). Additionally, Subchapter I vessels that carry limited quantities (20 percent of the vessel’s deadweight tonnage) of flammable and combustible liquid cargo in bulk, must do so in accordance with 46 CFR 90.05-35. Carriage of more than limited quantities of these liquids in bulk would require the vessel to be inspected under the applicable portions of 46 CFR Subchapter D (Tank Vessel).

Published 28May2019.

OSVs are restricted to service within the scope of the applicable regulations, which offer no relief for conducting lightering support unless they engage in lightering support for a tanker that received the oil from an offshore unit engaged in exploration, exploitation, or production of offshore mineral or energy resources (e.g. MODU, FPSO, etc.) AND the oil or mineral never reached shore prior to lightering operations as specified in the previous answer.

Published 28May2019.

The allowances and restrictions for an OSV to transfer fuel is determined by the transferring OSV’s tonnage.

Under current regulations and the U.S. Code, if the transferring vessel is as an OSV, < 500 GRT/6000 GT ITC, then it may transfer fuel to other vessels and offshore drilling or production facilities that are in support of exploration, exploitation, or production of offshore minerals or energy resources (including wind). However, OSVs, > 500 GRT/6000 GT ITC, may only transfer fuel from fuel supply tanks to offshore drilling or production facilities in the oil industry and not to any other vessels.

Please see the following flowchart. A pdf of the flowchart is also available here.

Read on for further information/insight related to these OSV categories...

The answers are found in 46 U.S. Code (U.S.C.) Chapters 21 and 37. Also, for OSVs, > 500 GRT/6000 GT ITC, we must refer to 46 CFR 125.115 for addition information.

46 U.S.C. § 2101 "General Definitions", defines an "Offshore Supply Vessel" as "…a motor vessel that regularly carries goods, supplies, individuals in addition to the crew, or equipment in support of exploration, exploitation, or production of offshore minerals or energy resources."

Paragraph (b)(1) under the "Tank Vessel Definition Clarification" found in 46 U.S.C. § 2101, states that an offshore supply vessel of less than 500 gross tons (6000 GT ITC¹) as measured under section 14502, or alternate tonnage measured under section 14302 of such title as prescribed by the Secretary under section 14104 of such title are deemed not to be a tank vessel for the purpose of any law.

OSVs < 500 GRT/6000 GT ITC
The "Tank Vessel Definition Clarification" found in 46 U.S.C. § 2101 means the "Carriage of Liquid Bulk Dangerous Cargo" rules of 46 U.S.C. § Chapter 37 do not apply to an OSV < 500 GRT/6000 GT ITC. Therefore, an OSV < 500 GT/6000 GT ITC, is allowed to conduct fuel transfer to other vessels only in support of exploration, exploitation, or production of offshore minerals or energy resources (including wind).

OSVs > 500 GRT/6000 GT ITC
OSVs, > 500 GRT/6000 GT ITC, are not exempted in the “Tank Vessel Definition Clarification” found in 46 U.S.C. § 2101 and the "Carriage of Liquid Bulk Dangerous Cargo" rules of 46 U.S.C. § Chapter 37 do apply.

However, 46 U.S.C. § 3702(b) exempts OSVs from the requirements of 46 U.S.C. § Chapter 37 only if they comply with the following paragraph:
(b) This chapter does not apply to a documented vessel that would be subject to this chapter only because of the transfer of fuel from the fuel supply tanks of the vessel to offshore drilling or production facilities in the oil industry if the vessel is—
   (1) not a tanker; and
   (2) in the service of oil exploitation.

Amplifying information regarding transfer of fuel on OSVs, > 500 GRT/6000 GT ITC, is found in 46 CFR 125.115 which states:
(b) Transfer of excess fuel oil from the fuel supply tanks of an OSV of at least 6,000 GT ITC (500 GRT if GT ITC is not assigned) to an offshore drilling or production facility will not cause Subchapter D of this chapter to apply to the OSV, provided that the vessel is—
   (1) Not a tankship as defined in 46 CFR 30.10–67; and
   (2) In the service of oil exploitation.

Utilizing the current regulatory exemptions of 46 U.S.C. § 3702(b) and 46 CFR 125.115, OSVs > 500 GRT/6000 GT ITC, are allowed to transfer fuel from the fuel supply tanks only to offshore drilling or production facilities in the oil industry.

All other type of fuel oil transfers would invoke the requirements of "Carriage of Liquid Bulk Dangerous Cargo" requirements of 46 U.S.C. § Chapter 37 and the "Tank Vessels" requirements of 46 CFR Subchapter D.

¹ Section 5209 of Pub.L. 102-587, as amended, refers to the specific U.S.C. tonnage measurement section under which the OSV is measured. For clarity the tonnage terms "GRT" for measurement under 46 U.S.C. § 14502 and "GT ITC" for measurement under 46 U.S.C. § 14302 are used in the answers of this FAQ. On December 18, 1996, the Coast Guard amended its regulatory definition of OSV in 46 CFR 125.160, establishing 6000 GT ITC as the alternate maximum tonnage for OSVs (61 FR 66613).

The answers to this FAQ are not all inclusive as it relates to fuel oil transfers. This FAQ does not address pollution prevention, notification requirements, transfer procedures, quantity of fuel, personnel or other operational requirements for the transfers of fuel or hazardous cargoes.

Published 11Jun2019; flowchart added 03Mar2023 and updated 04Aug2023.

OSVs certificated under 46 CFR Subchapter L are limited to the operations set forth by definition in 46 U.S.C. § 2101 and 46 CFR 125.160, which include regularly carrying "goods, supplies, individuals in addition to crew, or equipment in support of exploration, exploitation, or production of offshore mineral or energy resources." This definition has not been expanded to include towing. If an OSV wants to conduct towing operations, certain requirements associated with towing beyond those in Subchapter L must be followed to ensure safety of the vessel, waterway and crew.

   a. Any vessel engaged in towing operations is required to be under the control of a credentialed Master or Mate, with the proper endorsements identified in 46 CFR 15.805(a)(5), 46 CFR 15.810(d), or 46 CFR 15.535.

   b. Vessels 300 GRT or more meet the definition of a seagoing motor vessel and therefore are inspected under 46 CFR Subchapter I. OSVs 300 GRT or more that engage in towing need to be multi-certificated under Subchapters L and I. A vessel multi-certificated under L and I must meet the more stringent design and equipment standards of the applicable rules and regulations (including SOLAS, if applicable). Special stability requirements for towing vessels are outlined in 46 CFR 173.095 and 46 CFR 174.140. Additionally, vessels longer than 12 meters that engage in towing are required to meet the operational requirements generally outlined in 33 CFR 164.70 through 164.82.

   c. OSVs less than 300 GRT that engage in towing, other than on an occasional basis, need to be a multi-certificated vessel under Subchapters L and M. A vessel multi-certificated under L and M must meet the more stringent design and equipment standards of the applicable rules and regulations (including SOLAS, if applicable). Special stability requirements for towing vessels are outlined in 46 CFR 173.095 and 46 CFR 174.140. Additionally, vessels longer than 12 meters that engage in towing are required to meet the operational requirements generally outlined in 33 CFR 164.70 through 164.82.

Published 24May2019.

The frequency, but not duration, of towing activities impacts the above determination discussed in the previous FAQ. For example, 46 CFR 136.105(a)(5) allows for vessels inspected under Subchapters other than Subchapter M to "perform occasional towing." If more than "occasional towing" is to be performed, the vessel should be multi-certificated to include Subchapters M or I, as appropriate.

Published 24May2019.

No. The destination has no impact on any of the previous answers or decisions related to towing operations conducted by OSVs. However, the towing vessel and credentialed mariners would be required to comply with all applicable international convention requirements. The distance of the voyage may also change the number of required mates.

Published 24May2019.