"But I don't have my swim trunks..." you say, getting another round of giggles from all around.
"Oh, don't worry about that," one of the others replies. "We don't mind skinny-dipping." Feeling a little foolish, you realize they were all totally naked and not ashamed at all.
You don't need any more encouragement than that. Stripping down to your birthday suit, you wade out into the water...