I am an avid swimmer and have been able to deal w my dysphoria enough in the past to swim shirtless. I'm quite large chested and rather like the feeling of them floating, it's as close as I can get to them actually being not there currently. However, a place would have to be super private for me to do this.I don't know of anywhere id be comfortable. In my city females are legally allowed to be topless in public but few are because then they have to put up with all that sexualization of thier bodies.
I'm pre everything and def cannot pass without binding, often not even then, so if I went shirtless I'm sure I'd have to deal with the sexualization crap, which would bring on heaps of dysphoria.
I too eagerly await the day I can feel the ocean, a river, a lake, a pool on my bare chest.