Built for use as auxiliary craft, Otter primarily served as an at-sea training platform for junior naval officers, boatswains, reserve personnel and Sea Cadets at Canadian Forces Base (CFB) Esquimalt.

[1][2] Like other YAG 300 vessels, Otter was 75′ long overall, 18′6″ wide, had a draft of 4′6″, measured 70 tonnes, and was powered by twin 6-71 Detroit Diesel engines.

Otter was equipped with a Furuno 1831 navigation radar, with the display located in the wheelhouse.

Re-designated as YFP-312 (Yard Ferry, Personnel) in 1960, together with YAG 320 Lynx she was designated as a tender to HMCS Oriole in 1963.

[3] Later designated as YAG 312 Otter, she was regrouped under the control and operation of the Small Boats Unit (SBU) at HMC Dockyard Esquimalt where she was used for seamanship and navigation training until 2007.