[TAS] Season 1, Episode 12: The Ambergris Element
Rating: SKIP (For The Animated Series we use a simpler Watch or Skip rating)
Blandly straight-forward plot that seems to only exist because the writers thought it would be cool for Spock and Kirk to have gills and swim around.
Read more at Memory Alpha
Notes:

They don’t like air-breathers. They say the young ones saved them by turning them into water-breathers, but they don’t know how to reverse it

They try to suffocate them on some rocks, but one of the young ones points them out to Scotty, who was looking for them

Spock and Kirk look through an ancient land city that sunk in earthquakes. They figure out the way to change them back

The young ones want to start living on land. They wanna be up where they walk, up where they run, where they stay all day in the sun
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