Swimming skirts and dresses are a thing, though they're generally more for relaxing rather than heavy swimming, though you are right that they could be impractical. I've considered getting one, since they are more modest than a lot of other swimsuits, but I worry about it catching on something. HOWEVER, they have become a product mostly worn by landwhales trying to bury their double-fupas. Now I want one just to spite the obeasts, lol.