Open consultation

MGN XXX (M+F) Safety of Navigation: Guidance on towing requirements for offshore floating structures (excluding oil and gas infrastructure)

Published 20 January 2026

Summary of updates from first draft version:

• Clarification of merchant shipping jurisdictions
• Clarification on registration and classification requirements
• Application of Merchant Shipping (Load Line) Regulations 2018 and issuance of Load Line certificates and exemptions
• Wet storage chapter has been removed
• New chapter on Lighting, Marking and Signals requirements.

PDF version showing tracked changes also added to this consultation.

NB This summary will not appear in the final version.

Summary

This guidance note provides information for obtaining the necessary MCA approvals for towing floating and partially submerged structures, such as for use in the offshore renewable energy and aquaculture industries. It does not introduce new requirements to those already in place but is intended to direct the reader to the current relevant guidance and information.

Evidence for obtaining or meeting the following requirements must be provided to MCA prior to the towing of floating or partially submerged structures:

• Load Line Certification
• MARPOL
• Ballast Water
• Wreck removal
• Inventory of Hazardous Materials
• Emergency towing

1. Introduction

1.1 Technology in use in the marine environment continues to evolve and an increasing number of floating and partially submerged structures tethered to the seabed are proposed in UK Internal Waters, Territorial Sea and Exclusive Economic Zone (EEZ). These structures for use in the offshore renewable energy and aquaculture sectors for example, may be transported as cargo on suitable vessels or towed by vessels to a site in UK waters^{[footnote 1]} or EEZ, either from a UK port/harbour or from an overseas location. Towage requirements in the UK are well established and the below guidance is intended to provide operators with the necessary information for obtaining the relevant MCA approvals prior to towage operations. Certain legislative requirements may also apply once the structure is on site, and these will be applicable whether the structure was towed to location or delivered as cargo by another vessel.

1.2 The guidance set out below is applicable to those structures towed within UK waters and EEZ. Additional or different legislative requirements may be applicable if it is intended to proceed from UK waters to waters under the jurisdiction of another Administration. The MCA and other Administration(s) should be contacted prior to undertaking any such operation.

1.3 Operators should engage with the MCA as early as practicable and prior to any intended move, in order to ensure that the required information, survey and certification is in place. Locations of MCA marine offices - GOV.UK (www.gov.uk)

2. Jurisdictions

2.1 Certain aspects of floating and partially submerged structures fall under Merchant Shipping legislation and the exact requirements will be dependent on the specifics of the structure, operation and mode of delivery.

2.2 In general terms, if under tow, the structure and towing vessel(s) are required to comply with UK (and International, where applicable) Survey and Certification requirements, under MCA jurisdiction.

2.3 While under tow, floating and partially submerged offshore renewable energy installations are considered ships under the Merchant Shipping Act 1995.

3. Registration and Classification

3.1 There is no requirement for a floating structure to be classed with a UK recognised Organisation (Classification Society) (see MGN 322) or registered if it will be operating domestically i.e. towed to/from a UK harbour/port to/from a site within UK waters or EEZ. Whilst there is no legal requirement for the structure to be classed the safety standards and certification requirements must be met, and it therefore may be beneficial.

3.2 Vessel registration of the floating structure is required when operating on international voyages i.e. towed from a non-UK harbour to a site within UK waters or EEZ, or towed from a UK harbour to a site beyond the UK EEZ. For UK registration please contact the UK Ship Register. If the structure needs to be towed to/ from outside the EEZ. A Load line exemption or load line certificate can only be issued by MCA if the structure is registered in the UK or if the structure is owned by a UK citizen or if the company that owns the structure is registered in UK.

Note: the MCA as a regulator, cannot act as a consultancy service, therefore it is strongly recommended that an operator engages with a Classification Society and/or Marine Consultants.

4. Safety Standards and Certification

4.1 If the structure is to be towed beyond the limits of UK Categorised waters (as defined in MSN 1837 as amended) the Merchant Shipping (Load Line) Regulations  will apply as follows. The 2018 Regulations apply to all United Kingdom ships of 24 metres or more operating internationally and to non-United Kingdom ships of 24 metres or more while in United Kingdom waters and which are operating internationally. The 1998 Regulations apply to all United Kingdom and non-United Kingdom ships in United Kingdom waters which are operating internationally but which do not meet the size or weight criteria in the Convention, as well as to United Kingdom ships and non-United Kingdom ships in United Kingdom waters on domestic voyages. The structure must be surveyed and certified against these requirements by the MCA or MCA delegated Authority.

4.2 In most cases a UK Load Line Exemption Certificate for a towed object will be applicable. The following requirements must be in place for a Load Line Exemption:

    4.2.1 Gross tonnage calculation. If a vessel or structure is registered in the UK a tonnage certificate will be required in accordance with The Merchant Shipping (Tonnage) Regulations 1997. Guidance available from: Tonnage measurement of UK ships: Authorised organisations - GOV.UK (www.gov.uk)

If the structure is not registered the gross tonnage must be known since other regulatory requirements are determined by the tonnage of the tow. The operator must provide evidence of the gross tonnage calculation and MCA will accept a written declaration from a marine surveying consultant of appropriate professional standing e.g. structural engineer or a Classification Society. The declaration should detail the methodology and calculation used to determine the tonnage which should be one of those laid down in the tonnage regulations for a “vessel” of that type.

    4.2.2 Structural integrity. A declaration or statement from builder/ consultant / insurance that the structure meets the appropriate standard for its intended function and area of operation. This should be supported by an assessment of the structural integrity to show it is able to withstand the expected metocean conditions.

    4.2.3 Stability. The structure must have sufficient reserve buoyancy for the intended area of operation (including as a towed object) and that during the tow there is sufficient stability to prevent capsize and becoming a navigational hazard. The object should have sufficient stability during the tow to ensure that under all reasonable and foreseeable scenarios manual intervention is not required in order to maintain the structure in a buoyant and stable condition. The structure should have a “waterline” mark, clearly visible from the towing vessel so as to easily identify if the structures buoyancy or stability is changing during the tow.

The stability assessment should be conducted for all stages of the project, for example: under tow, during assembly and final operational status on site. The stability assessment should be undertaken by appropriately qualified and recognised persons (e.g. Classification Society, Marine Consultant / Naval Architect of suitable professional standing).

    4.2.4 Satisfactory survey by MCA or authorised body. UK Load Line certification will be valid for a single “voyage” to the final location^{[footnote 2]}. Subsequent planned move(s) will generally require new certification and may also need further survey of the structure, by MCA or delegated Authority. MCA-approved ROs can issue UK and International Load line certificates. The UK load line exemption certificate can be issued by the MCA only, however this can be based on surveys by an approved surveyor.

            The operator should have in place procedures for routine inspection and maintenance of the structure and provide a statement verifying that the structure remains “seaworthy” and fit for any intended move.

            MCA will consider on a case-by-case basis whether a certificate of extended validity can be issued to cover subsequent movement of the structure for up to five years. This will be subject to the above, and the operator agreeing to bring the structure into port / sheltered waters for survey at intervals agreed by MCA (no more than five years).  Dive survey may be considered subject to detail.

            Where there are safety related systems or equipment on the structure, in addition to any mandatory requirements; for example, firefighting equipment or lifesaving appliances, it is MCA policy that this equipment is maintained in proper working order. 

            MCA may also carry out an inspection of the towing vessel to ensure compliance with relevant legislation and guidance including MGN 592 (M+F) (as amended)  anchoring, mooring, towing or hauling equipment on all vessels.

4.3 MGN 468 (M) Voluntary Towage Endorsement Scheme, as amended - although applicable for smaller vessels, provides guidance on competence standards and the specific knowledge, understanding and proficiency needed for safe towage operations.

5. MARPOL Requirements

5.1 MARPOL requirements are generally applicable to floating objects, while under tow and on station. The exact requirements with respect to Survey and Certification will depend on the details of the structure, its tonnage and the equipment on board, however, where there is a risk of pollution from fuel, garbage, sewage, emissions or any other pollutant, the relevant Annex of MARPOL (and associated UK SIs) will apply.

5.2 Where MARPOL survey and certification is required, MCA may be willing to waive requirements for annual endorsement, subject to detail. This will only be applicable in UK waters.

5.3 If the structure is operating exclusively within UK Categorised waters, alternative requirements may be applicable with respect to air pollution and anti-fouling requirements:

MGN 646 (M+F) Engine emission standards applicable to inland waterway vessels

MGN 647 (M+F) Alternative to the IMO MARPOL Annex VI tier III standard engine

MGN 676 (M) Unmanned non-self-propelled barges – MARPOL Annexes I and IV Exemptions

MGN 398 (M+F) Amendment 1 Merchant shipping anti-fouling systems regulations

6. Ballast Water

6.1 If operating internationally Ballast Water Convention requirements apply irrespective of tonnage, and specifically depends on the ballasting capabilities and arrangements of the structure(s). See MGN 675 (M+F) and MSN 1908 (M+F) The Merchant Shipping (control and management of ships’ ballast water and sediments) Regulations 2022.

7. Wreck Removal

7.1 In accordance with the Nairobi International Convention on the Removal of Wreck 2007, the registered owner of a vessel, including floating platforms (except when on location), with a gross tonnage of 300GT or more must have financial security or insurance to cover the costs of locating, marking and removing wrecks. A certificate issued by MCA or another state party to the Convention confirming that insurance is in place is required. For applications to MCA, evidence of insurance meeting the requirements of the Convention, evidence of tonnage, and fee must be submitted to MCA using MSF3241 e-Application for UK compulsory insurance certificate – GOV.UK (www.gov.uk)

8. Inventory of Hazardous Materials (IHM)

8.1 The UK Ship Recycling Regulations may apply, and where required an Inventory of Hazardous Materials, an Inventory Certificate and Ready for Recycling Certificate should be provided. MGN 633 (M+F) as amended provides details.

9. Emergency Towing

9.1 In the event a floating structure breaks free from its tow or moorings and becomes a floating navigational hazard, arrangements must be in place to allow for emergency towage and for the recovery of the structure to a suitable location. These arrangements will be reviewed by MCA as part of marine licence or consent consultations with the applicant and through the devolved marine licensing authorities.

9.2 In these circumstances, the concept of force majeure would apply, and MCA survey and certification requirements would not be applicable, to the extent necessary to bring the structure to a safe haven. However, it should not be assumed that a Port or Harbour Authority would allow a structure to enter its area of jurisdiction.

10. Lighting, Marking and Signals

10.1  During towage operations towed structures must only display signals required under the Convention on the International Regulations for Preventing Collisions at Sea, 1972 (COLREG).

10.2 Any Aids to Navigation (AtoN) fitted to floating structures must be extinguished during the tow to avoid confusion with any signals displayed as per COLREG. This should include any lights, hazard warning signals, and electronic AtoN including AIS broadcasting Message 21.

10.3 Any signals displayed whilst the structures are in wet storage will need to be discussed with the relevant General Lighthouse Authority who may require all AtoN, and especially AtoN broadcasting AIS Message 21, to be extinguished whilst the structures are temporarily stored.

More information

UK Technical Services Navigation
Maritime and Coastguard Agency
Bay 2/20
Spring Place
105 Commercial Road
Southampton
SO15 1EG

Telephone: +44 (0)203 817 2554

Email: navigationsafety@mcga.gov.uk

Website: www.gov.uk/mca

1. Under the Merchant Shipping Act 1995 s.313, ‘UK waters’ means the sea or other waters within the seaward limits of the territorial sea. ↩

2. The coordinates confirmed in the development consent or marine licence. ↩