Aquatic subtype would need to have amphibious, not water breathing.  I prefer water subtype and water breathing.  (A little odd, though, since their "cousin" the copper dragon is earth subtype.)
Definitely cleric and domain spells.  Since they favor "conjuration/summoning and alteration" (transmutation, I guess) spells and are CN and water-related, maybe Chaos, Water, and Creation domains?  Not a lot of transmutations in there, but lots of conjuration and some "alteration-like" abjurations.
Definitely Swim.  Maybe Spellcraft since they like to use spells more than melee.  And Appraise for valuing the gifts they receive.  I wouldn't mind a small racial penalty to Sense Motive.