I'm not sure I can think of something for all of them, tbh... fashion design is hard.

Maple: Something with shorts. Ultimately unclear
Clarabelle: White one piece w/ little skirt thingy... I got art of it, actually.
Victoria: An old-timey men's swimsuit, the kind with the stripes.
Freya: Another one I got art of! Two piece, light blue and white striped top, and a frilly-looking skirt-ish thing in the same colors. I used a drawing by MidniteMorty as a reference.
Ysabel: Sundress, of some sort. She's here to read, not swim...
Sharla: Something sarong-y, I think that's a type of swimsuit.
Yuzu: One of those red lifeguard swimsuits. She's working at the beach.