The swim section of a triathlon often takes place in open water such as a sea or a lake. Triathlon rules state that competitors wear a wetsuit under certain conditions, mainly to protect them from the cold water temperatures. When competing in a triathlon event, wear your competition clothing underneath your wetsuit to make your transitions much quicker.Most serious triathletes own a suit specially designed to wear during competitions. Tri-suits are usually made from lightweight fabric to avoid weighing you down. You can choose full-body suits, ones with short arms and legs or separate tops and bottoms. Most suits are quick-drying and anti-chafing to keep you comfortable throughout the race. Look for additional features such as breathable fabric, ventilation, sun protection and hidden bust support for women.Women’s tri-suits are specially designed to fit the female shape, and come in extra small to extra large sizes. If you have a larger bust, look into suits with extra support in this area, or you may prefer the two piece option as they sometimes provide a better fit. Opt for a crop top with hot pant-style shorts, or go for a longer top and cycling shorts if you prefer more coverage. Also, consider wearing a quick-drying sports bra underneath your tri-suit. Look for triathlon-specific sports bras that compress your bust and won't bulge underneath your wetsuit.Men can opt for tri-suits or choose shorts matched with tightly fitted or slightly looser tops. If you feel uncomfortable in a full-body suit, wear shorts underneath your wetsuit and pull on a T-shirt during your first transition. Putting a T-shirt on will take a few seconds which you may not want to spare; however, a dry shirt may keep you more comfortable throughout the rest of the competition.Consider shaving your body hair and applying petroleum jelly to certain areas. Shaving reduces friction and can help you to remove your wetsuit quickly, while petroleum jelly can reduce uncomfortable chafing -- especially on the shoulders, around the armpits and the groin area.