HMS Seahorse was a 10-gun fireship of the Royal Navy in service from 1694 to 1698, when it was sunk as a breakwater.

It was first used as a fireship, and then was repurposed into a water boat to carry freshwater to larger warships.

[1] The wreck of the ship was used as a part of the retaining wall at a depth of about 30 feet (9.1 m).

[2] In 1871, the wreck of Seahorse was discovered while alterations to Chatham Dockyard were being made.

It was subsequently excavated for its lumber, the best of which was sound enough for use at the dockyard with the rest being sold at an auction by the Admiralty.