Seahorse Mercator is a variant of the design.[1] The ship has a displacement of 165 tons, a length of, a beam of, and a draught of .[1] Propulsion is supplied by two Caterpillar 3304 diesels, driving two propellers.[1] Maximum speed is, with a range of at .[1] Seahorse Mercator is run by a crew of five plus three instructors, and can carry up to eighteen trainees.[1] Radars include a Furuno FE 606 navigation radar, and a Decca Bridgemaster ARPA navigation radar.[1] The vessel is unarmed.
Seahorse Mercator was built by Tenix Ship Building Western Australia for DMS at a cost of A$4 million. The vessel was launched on 15 October 1998.[2] The Canadian Forces Maritime Command's s were built to a modified variant of Seahorse Mercators design.[3]
Seahorse Mercator conducted sea trials during November 1998, with handover to DMS and the RAN on 26 November 1998[4] She was assigned to the naval base, and replaced the as the RAN's Sydney-based navigational training vessel in December that year.[2] Since then she has mainly operated in the Sydney area[1] and has trained RAN personnel and sailors from other navies in coastal navigation, ship handling and watch keeping procedures.[5]
Seahorse Mercator has a secondary role as a mine countermeasures craft.