Pee-pee ruins the seams in wetsuits. I thought everyone knew that. So I can honestly say I've never done it. It's a huge hassle but I head for the beach to unzip the wettie when it's time to answer the call.
I never wear one in Singapore anyway; you only need wetsuits in really cold places like Queensland.


As for cleanliness - come on, sflack! A wetsuit is constantly having sea water run through it while you're wearing it (depending how much you wipe out), and it gets a good rinse after sailing, so I'd say it's unnecessary to wear undergarments, except as an extra layer of insulation.
Nice vid, by the way, and next time there's no need to add the Red Bull stuff - the original footage was rad enuf!