The Ambergris Element
Kirk and Spock mutate into water breathers, and must convince the native civilization not only to reverse the effect, but rescue them from an earthquake.
Pretty darn good for an episode that possibly began as the pitch, " Kirk and Spock turn into fish." A simple story but very Star Trek, wherein a new phenomenon is discovered, and friendship and cooperation form after an initially hostile confrontation with an alien race. Cohesiveness is a rarity in TAS but can be seen here. The swimming animations are a delight, especially when we see Kirk and Spock headed in one direction, then a shot of the sea monster, then our officers swimming in the other direction. The Aqueans are somewhat convincing but not fleshed out. But Kirk wins best line again with, " I can't command a starship from inside a fish tank!" Too true, but his underwater adventure is a bright spot in this series.
Spock Saves the Day: Spock doesn't do anything really useful, but never once leaves Kirk's side, and helps get the antidote.
Oops: The lack of any unique insights into this experience is glaring. He's usually enthusiastic about such things.
Developments: Add "breathing under water" to super powers gained and as quickly lost, then forgotten.