Built in 1966 at the National Steel and Shipbuilding Company shipyard in San Diego, the ferry began service on July 20, 1967, and normally ran on the Seattle–Bremerton route or the Anacortes–San Juan Islands run.

[2] The vessel traveled north along the Pacific Coast in June 1967, but was delayed by a severe storm near San Francisco, California when it broke a temporary breakwater.

[5] The ferry was not able to enter service after arrival because of an ongoing labor dispute with the local chapter of the International Organization of Masters, Mates & Pilots.

[12][13][14] The Hyak primarily served as a standby vessel for the rest of the fleet and was considered for experimental conversion to use hybrid diesel-electric generators until the plan was scrapped in 2015.

[18][19] The vessel's horn was donated to Climate Pledge Arena, where it is used by the National Hockey League's Seattle Kraken every time they score a goal during home games.

[21] On April 14, 1986, the Hyak ran aground in Anacortes, Washington after a navigational error made by the crew, placing the ferry in shallow water above a reef.