Sturgis stop

Maybe a bro out there can solve a mystery for me. A few years back we were at Sturgis on the main drag (I think it was 1998). We walked past a store front where this wasted due was standing with about 30 piercings all over. The sign in the window said "Adult swimming lessons downstairs. Must be over 21". My 16 year-old son was with me, so I never got to check it out. I thougt I'd heard them all, but I have never heard of adult swimming lessons. Can somebody tell me, using phrases acceptable to a people-friendly site so as not to tick off CD, what the hell that is? By the way, if you do an on-line search of Photos- 1998 Sturgis Rally and look in the "general" category, you will see a shot of the wasted due and the actual sign in the window. Incidentally, my son still considers that the best trip we ever took. It beat the hell out of Disney World!