G string swimwear

[PSDave]

If you are talking about an actual g-string and not a thong anything you get is not really designed for active swimming - especially diving. Wearing one for protecting the goods while snorkeling or scuba diving is a wise idea -- no use tempting a hunger fish!
I have one that I have worn for that purpose that ties on. I like it cuz it can be tied tight around the waist and is secure.

[Bede735]

I guess the best idea is to test it out. Instead of swimming naked in a sea or river, wear one and see if it holds up. If it doesn't, then you're back to the original intention.