Re: school swimming
This may sound geeky, but you could wear your underwear underneath your bathing suit (but only briefs, 'cause boxers don't hold stuff down)! I would have never tried this, but one time I bought a new bathing suit and the netting inside was really itchy, so I thought wearing my briefs would keep the discomfort down. That worked, but it also completely hid my erection (since I always get at least one when I swim). So try that if you really want to hide it...