One of the first questions people ask when they are new to this stuff :). Few things to say here:
1. First you might want to put something under your wetsuit if you are cold. If your wetsuit is too thin for the water you are throwing yourself into put on a thin wetsuit top, a thermal lycra or neoprene shorts and then your wetsuit. You will get some extra insulation and will stay warmer.
2. The most common “what to wear under wetsuit” question is just a polite way of asking “omg, should I be naked??”. Yes, you should. It’s not like a law or something but most people don’t wear anything under their wetsuits. OK, if you know you will be changing in a public place, you are really shy, clumsy with a towel, don’t have a poncho… then put on a normal bathing suit. Don’t use boardshorts (however cool they might be to you). They’ll get all wrinkled up and very uncomfortable. Throw on some dickstickers, nuthuggers… Oh, also if you are renting a wetsuit and you don’t like the idea of your private parts rubbing with places where other people’s private parts rubbed before – also use bathing suit.
3. Third and final reason for wearing something under your wettie is wetsuit rash or wetsuit chafing. In places where there is a lot of movement your skin rubs against the neoprene and after awhile it will get sore. The usual suspects for this are your neck, armpits, behind the knees, ballsack… with neck and armpits being the most common. To prevent this:
- wear a lycra,
- wear a bathing suit,
- use anti-chafing gel/cream.