He'll need training, (as noted in some of the other posts), but being blind isn't a whole lot different than what a lot of us dive in on a regular basis.
This probably isn't something you want to do on a coral reef, but should be pretty exciting in a lake or quarry where the features aren't very dangerous or delicate.
With a good briefing, a blind diver could easily follow the bottom down to the edge of a wall, turn right, follow the wall to a big log resting on it, then follow the log down to my favorite logpile.
Since the vis generally ranges from bad to terrible, the blind diver would be on pretty much equal ground with his buddy.
Terry