[HoneyBadger]

Burnsaber: I'll draw you an otter and a porpoise by this weekend. Not a problem.

I very much like the idea of Oceania being powerful physically in the ocean, and then powerful magically on land (in that they could have additional ritual spells for land, like Hurricane).
'Mist' is another good idea.

Another idea that strikes me as to how to differentiate Oceania would be to base it somewhat on the end of Clash of the Titans, where Proteus releases the Kraken. So maybe give Oceania a powerful amphibious endgame summon that can only be cast on land?

To give you a "for instance", the Cyclops in the Odyssey was supposed to be the son of Poseidon, so maybe something there?