Funny, I was just thinking about this, as new swimsuits keep popping up in my daily "buy our new stuff!" emails from stores.
Like you, I really avoid beach and ocean vacations because of sun concerns. But I do enjoy it when I'm willing to go to the hassle of sun protection.
I have a slightly retro one-piece, similar to some that folks have posted: straight across the chest, halter tie, not high cut at the legs, solid black. I think it's a very versatile shape for many body types.
When I do swim, I wear a rash guard top or, ideally, a full wetsuit. I went snorkeling for hours in Hawaii -- my brother got married there last year and I couldn't stay away from the beach for that special occasion! -- and I rented a full wetsuit even though it was warm enough for a bathing suit. It was pleasant to have the extra warmth and flotation, and I didn't have to think about sun.
I am so tempted by the long-sleeve swimsuits (almost like lightweight wetsuits) that are a fringe trend these days. I'd love one of the Cynthia Rowley wetsuits with a dark floral pattern, but I can't justify the cost for something I do so rarely. A few that I really like are in Finds (the red ones also come in navy, a better color for me).