While exploring the water planet Argo, Captain Kirk and Mr. Spock are transformed into water breathers
by the planets inhabitants, the Aquans. In order to return to their normal human selves,
they must enlist the help of the Aquans to capture a giant sur-snake, whose venom holds the antidote.
Written by Margaret Armen, who also wrote the original series episodes "The Gamesters of Triskelian",
"The Paradise Syndrome", and "The Cloudminders". This is a great episode which takes full advantage
of the animated format.