The problem isn't so much that we have no faith anyone can swim (animal mages would do just fine normally) but that the place is cursed! If you don't on out of there fast, the curse will stick. The people who live there seem friendly enough but are mostly just trying to usher the newbies out once they're sure they're okay, so he'll have to come back to the sea monster town later.

Observably, most of them seem to have a cute accent of unclear origin. The mermaids are friendly (differentiated from the merrow in other areas, who eat human souls), the naga are more stoic and willing to be firm but are still friendly enough-- they're a guardian type of species after all, and the cecaelias don't particularly seem interested in giving attention to newbies unless they outright start harassing them, in which case they'll take harsh vengeance (but you had it coming).

Characters will notably be stopped from eating anything regardless of who or what they are, and scolded for doing so if they ever want to go home again. It's unclear how much more of the past magics of the fairy realm are still in place, but there was decidedly once a time when eating fairy food could make it impossible to return to the human realm. Camelot has been specially carved out and made human-friendly, but the further into Elphame territory they get, the more a risk it becomes.

I hope this is helpful at least, even if you cant get a full exploration in yet!