The pool session.
This is probably the first time since childhood swimming lessons you'll be asked to participate in a class in a bathing suit. And for those who are not avid swimmers or pageant models, this may be one of the toughest parts of your open water class.
The bathing suit. One piece? Two piece? Shirt over? Shorts over? Full wetsuit?
Ideally, if you have a light wetsuit (1mm or 3mm shorty or full) it's not a bad thing to wear in the pool. Though the pool is usually 82 - 86 degrees Fahrenheit, water pulls heat away from our body much faster than air, so women without extra insulation can become chilled during a two hour pool session.
Bikini? Not really the best bet. In the scuba industry, chances are you'll have a predominantly male staff working with you in the pool. Distraction for this group rates high when a female student dons a bikini. Let them focus on scuba instruction.
One piece. Much better choice than the bikini, however, you are going to be doing two skills which deserve some attention in this article.
The first skill, Alternate Airsource with ascent to the surface. You'll be giving the other person your alternate airsource, then reaching with your right hand to grab the shoulder strap of the BCD for ascent. This can be uncomfortable if matched with an unknown male student if too much cleavage is revealed.
The second skill, Tired Diver push, requires your buddy to fully inflate you and have you lie on your back while they put their regulator in their mouth, one of your feet on each of their shoulders and push you towards the edge. Their head is right in line for a stellar crotch shot, and now is not the time for any creepage or slippage from a bathing suit.
My favorite outfit is a pair of board shorts with a rash guard top. I usually wear a swimsuit underneath, for added modesty, as a rash guard is not opaque enough without an undertop. The rash guard provides chest coverage, as well as preventing chaffing from the BCD straps. The board shorts make all underwater swimming free from the worry of a swimsuit out of place.
If a bikini is available, it's a great underlayer, as any needed stops at the restroom are easier in a two piece.
The pool session.