In 2269, an amphibian Elysian councilor wore a water mask, when she visited aboard the USS Enterprise, while the ship was stranded in Elysia. (TAS: "The Time Trap") Later that year, and after being mutated by the Aquan surgo-op, James T. Kirk and Spock became water-breathers and had to be kept in an aquarium in sickbay. While en route to the surface of the ocean planet Argo to discover the source of their mutation, they wore an aquatic support apparatus so they could breathe. Similarly, the Aquans wore water masks while they visited the USS Enterprise. (TAS: "The Ambergris Element")