The offshore support vessel Topaz Tangaroa has been purchased by the UK Ministry of Defence for conversion to a Multi-Role Ocean Surveillance (MROS) ship.

She arrived at Cammell Laird shipyard on Merseyside in mid-January 2023 for conversion and will serve in the Royal Fleet Auxiliary renamed RFA Proteus.

Proteus will be dedicated to safeguarding critical seabed infrastructure and will act as a ‘mother ship’, operating remote and autonomous off-board systems for underwater surveillance and seabed warfare.

The vessel was purchased for £70 million from Topaz Marine, a subsidiary of P&O Maritime.

This modern 6,000-tonne ship was built in 2019 for work in the offshore oil industry supporting construction, maintenance and inspection work and is equipped to operate autonomous submersibles.

VARD designed her and the hull was built by their Tulcea shipyard in Romania and fitted out at their Brattvaag facility in Norway.

The ship has diesel-electric propulsion driving azimuth thrusters at the stern. A dynamic positioning system with powerful twin bow thrusters allows her to hold a precise stationary position when working over subsea installations.

She also has good sea-keeping abilities, low fuel consumption and will be well suited to her new role.

A ‘moon pool’ – a vertical shaft in the centre of the vessel provides a sheltered way for robot submersibles to be launched or recovered in high sea states.

The 98.1m ship also has a flight deck, a heavy duty crane, 1,000 square meters of cargo space and a working deck aft.

She has previously been employed on undersea construction in the North Sea and more recently on a major wind farm project off Taiwan.

The conversion by Cammell Laird should be relatively straightforward, primarily painting her grey and the addition of light weapon mounts and military communications equipment.

Otherwise, the ship is already in good shape for her new role and RFA Proteus will enter service in the summer.

Proteus will be operated by a small RFA crew of 26, augmented by about 60 RN specialists responsible for the undersea surveillance, survey and warfare systems.

It is expected she will primarily operate from Portsmouth Naval Base, although RFAs are not usually permanently base-ported like RN vessels.

Photo by Hans Esveldt/

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