My wife loves to swim naked, which we regularly do at nude swim events.
Apparently she (and according to her, all women) seem to like the way her breasts (C-cup) float in the water when swimming naked.
Every sunday morning, she goes swimming at our local pool (with swimsuit).
Usually the same people show up to swim some laps and at 40 she's at least 20 years younger than most of the others (mainly guys). I sometimes join them too, but mostly to keep an eye on our kids.
The tanktop bikini she wears during those swims, is white/pink coloured, without preformed cups.
Not showing a lot of cleavage, but her nipples are always protruding.
Some weeks ago, I told her that her nipples and areolas where showing through the fabric when standing in the sunlight. Her reaction to this was quit surprising. She said "the bikini is not yet that old and as long as it's not completely seethrough, I'm not yet going to buy a new one. Also there are only familiar people swimming on sunday morning and I'm in the water most of the time anyway. And in case some of the guys get a nice look, they'll have something to gossip about when I'm not around
"
Personally, I'm not complaining since I love to expose my wife's naked body ... so I let her be and love watching the "old guys" taking peeks at her chest.
@britrob : looking at my wife's C-cup I was surprised you would call a C-cup "small". Starting from a larger B-cup till larger C-cup, I would definately call them midsized. Luckily, I prefer small to midsized cup sized. Definately prefer them of the DD's of my SIL.