I pee in pools, oceans, lakes, rivers, pants, diapers etc. I am IC and can't help but pee in these places and, no thanks, I'm not putting a clamp on my penis. Also, if I'm in these places I'm usually swimming, surfing, kayaking, sailing, scuba diving, skin diving, etc., so I need to be able to move.
This thread does bring up a dilemma for when you are at the beach, on a boat or in a pool, but not actually going in the water right away. Here's how I deal with it. If I'm in this situation and I know 100% that I'm not going in the water (this is rare for me), I'll wear my regular diaper. If I'm pretty sure I'll be out of the water for a given set of time, but going in at some point (less rare for me), I'll wear a Depends pull-up under my shorts, sometimes two Depends. It's fairly easy to wrap a towel around my waist and discreetly remove my pull-up when I'm ready to get in. Usually I'll make a full change of shorts so it's clear to others that I'm changing my clothes. Lastly, if I'm going in right away, which is usually the case, I won't wear any protection...or maybe a swim diaper (see below).
I have pooped in the ocean (many times) and come close to pooping in public swimming pools (on my rush to the bathrooms) so I have worn a swim diaper on a number of occasions. My problem with the swim diapers I've tried is that I'm often around other people and I don't like the bulkiness of them. If anyone has some suggestions for a lighter weight swim diaper, I'd appreciate it.