I've done St. Anthony's every year for the past... 4 years? Great race, one of the best in the U.S. IMO. The swim is "deep water" in that you'll never be able to touch the bottom until you get pretty close to shore but the water is fairly shallow (maybe 7-8' for the sprint, 10-12' for the olympic) and if the water is calm you can see the bottom. Wetsuit legal seems to be a 50/50 proposition. Seems to depend on the weather the week prior to the race.

Edit: oh yeah I'll be there again this year.