Union Manta is a vessel of 75m in length overall, with a breadth of 18m and maximum draft of 6.6m. Capable of towing, anchor-handling, buoy handling, offshore supply and ROV support, she has a large clear afterdeck with a cargo capacity of 800 tonnes. Internal tanks and transfer equipment are provided for the transportation of a wide range of liquid and dry bulk cargoes.

Two Wartsila main engines running at 750rev/min deliver a total of 20,000bhp (2 x 7360kW) to drive a pair of controllable pitch propellers and two shaft generators. The 4.1m propellers rotate within fixed Kort nozzles.

Twin 'high lift' flap rudders can be operated independently or in unison. Four transverse thrusters, two forward and two aft, are each driven by a 883kW electric motor.

This arrangement gives the vessel excellent manoeuvrability and a bollard pull of over 210 tonnes.

A massive Brattvaag/Rolls Royce triple drum towing and anchor-handling winch is installed.

All three drums have a maximum brake holding load of 625 tonnes and line pull of 500 tonnes. The largest drum can accommodate 8,000m of 72mm diameter steel wire rope, and the smaller drums 3,000m. Two tugger winches have a line pull of 65 tonnes and split drum stern roller has a maximum safe working load of 500 tonnes. A stern mounted 'A' frame by Hydralift has a safe Union Manta is capable of working in deep water with a towed plough to bury pipelines of 2m diameter and to carry out anchor-handling operations in water depths of up to 3,000m.

A dynamic positioning system is fitted that allows the vessel to maintain station to an accuracy of 1m in rough seas and in winds up to force 6. This facility in conjunction with the 'A' frame enables Remotely Operated Vehicles to be deployed to carry out a wide range of underwater tasks in deep water.

Accommodation is available onboard for up to 37 persons, including crew and specialist personnel, in 17 single and 10 double cabins. The vessel is air-conditioned throughout and has two fully equipped offices and a fully fitted and well fitted galley.

Union Manta is scheduled to operate in the Brazilian offshore oilfields on long term charter to Heerema. URS expect to order a second tug of a similar type and dimensions in 2004.