Wait, would a were-fish be even possible? I don't think so. I mean, I can't think of any fish with true violent tendencies--sharks don't count because it's more of a hunger reaction that sets them to actively hunting than anything truly intentionally violent--and if you were on land on the full moon, that's pretty much Instant Death. Plus, what if you were waaaay out in the ocean when the sun came up and you shifted? Heck, even being in the shallows would be dangerous because shifting is supposed to be incredibly tiring and you'd zonk out in the water and drown!

So, no, I don't think that'd work.

...Maybe some kind of sea bird, like a seagull or a pelican or albatros?

-- Rosy the Cat