This would certainly be a great way to liven up a fundoshi party!
Look at all the smiles, wet bodies, and translucent fundoshis! A nice hot cup of sake or two afterward and some clambering out of wet loincloths would no doubt finish off the party with a flourish. Events like these tend to be community-building and male bonding in nature; releases of pent-up energy in a positive way that expands goodwill and warms hearts. We could definitely learn something from this aspect of Japanese history and tradition -- instead of isolating ourselves from one another, we should get half-naked and frolic about in cold water; social barriers erased, fun at the forefront, shame and self-doubt left on the shore with our clothes.