That sounds like an accident (no pun intended) waiting to happen. What it you don't purge [your reg!] fast enough? Gravity would then bring the warm rush up towards your head.ThatsSomeBadHatHarry:l8ike i said, i have th e pinnacle polar and it is a semi dry. i love it so far. you can prime it with warm water that will stay with you (though i haven't even needed to do that) so far i've used it in 54 degree water and have been very comfortable so far. as for the peeing, i go before the dive and if i have to hold it, i do.
there is another method for going in a semi dry: go vertical (with head down) and purge your reg through your neck to send the water out your ankles.
I'll pass. Wetsuit 7mm, or drysuit, for me.