Merfolk ideas?

[Ren]

So I'm finally getting up to speed on this campaign I have planned but one of the major races I have planned are the merfolk; denizens of the deeps etc...
In the campaign I am planning on having an influx of arriving in Miami and I would like to get some ideas and suggestions on how they might work on how they might be worked up.
I had originally thought about making them another element of the Fae Courts but decided they should be their own group with their own abilities including transformation from a marine animal form to a human form and have a hybrid form in between.
And I'm not talking Disneyfied little mermaids here, I'm talking the Nymphs, Nereids and Sirens of Greek and Roman mythology; creatures as fickle, dangerous and ever-changing as the sea.
I'm also going to be working on were-sharks, were-gators and possibly even were-rats to go along with the campaign background.

I'm figuring a good blanket catch for all of the Merfolk and marine-weres would be "Child of the Sea" which requires them to spend at least one day in the sea for every day the spend on land (possibly more) but they cannot exceed X number of days on land (based on physical damage track...whatever its called, I don't have my book handy) or they start taking damage, something akin to asphyxiation.

[Sanctaphrax]

There are several takes on merfolk on this board already. The Generic NPC thread contains Fomors (semi-canonical fish people), Sirens, Nymphs, the Leviathan, and some other aquatic stuff. The various more obscure mythical creatures thread has much of the same, plus another take on Sirens, the Kraken, and some different other stuff.

They may not be exactly what you're looking for, but I think they're worth checking out.

[Tsunami]

I'm figuring a good blanket catch for all of the Merfolk and marine-weres would be "Child of the Sea" which requires them to spend at least one day in the sea for every day the spend on land (possibly more) but they cannot exceed X number of days on land (based on physical damage track...whatever its called, I don't have my book handy) or they start taking damage, something akin to asphyxiation.

Why make it so complicated? Simply use "Fire" or maybe "extreme Heat" as their catch.
the Need to return to the Sea can easily be modelled through compels on the High concept of such creatures.