wrist support while swimming?
Doubtful that anyone would call DQ on him unless he's got some web-fingered glove on.
White medical tape should be all he needs to power through the sprain during the swim and on the bike. Should last for a sprint and then some.
Greatness is only achieved by those who perpetually raise the expectations of themselves to the point where it ruins their life.
After my cast was off from the fracture in my thumb last year, I swam with it taped. The white medical tape worked decent, but I used duct tape in the open water as I found it lasted a bit longer when wet. The white stuff came off in the pool after about 1000m.

I think an official could make a case that such a brace is a swim aid: it would aid the rigidity of your wrist during the downstoke and would add propulsive drag. If not, I'd wear one on each wrist. As SueR wrote, tape would be fine, and I know of no rule that says he couldn't wear a brace on the bike.
Good stuff - Thanks for the input









My idiot brother in law sprained his wrist a few weeks ago. (I'll call it a sprain- doc says nothing is broke.) Against my advice he is going to pursue the sprint we've been training for in 2 weeks (first for both of us). I assume he can't wear anything on his wrist during the swim, right? It seems to me that even a simple wrist support could aid his progress and would not be allowed. I would also assume he could wear the support on the bike, right? thanks for your input-
*he does not plan on doing any other tris in the near future, I've urged him not to do it and still might not if its too painful