Seahorse Mercator is a navigational training vessel operated by Defence Maritime Services under contract to the Royal Australian Navy (RAN).

[2] Seahorse Mercator was built by Tenix Ship Building Western Australia for DMS at a cost of A$4 million.

[2] The Canadian Forces Maritime Command's Orca-class patrol vessels were built to a modified variant of Seahorse Mercator's 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 HMAS Waterhen, and replaced the Attack-class patrol boat HMAS Ardent as the RAN's Sydney-based navigational training vessel in December that year.

[2][5] 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.