There's this really old animated kids movie I used to watch when I was little about these sea creatures that were "magic" because they could talk by wearing these medallions around their necks. I can't remember very much of it but it's going to absolutely drive me nuts until I figure out what that movie was called.

Could it be Water Babies? Click on this link for more info: The Water Babies (1978). Stars: James Mason, Billie Whitelaw. Director - Lionel Jeffries. Children's Film. Moria - The Science-Fiction, Horror and Fantasy Film Review. (http://www.moria.co.nz/fantasy/waterbabies.htm)