Regular practice and competition swimwear

Men

Men's most used practice swimwear include briefs and jammers. Males generally swim barechested.
There has been much controversy after the Beijing Olympic Games in 2008, when many Olympic swimmers broke records an unprecedented number of times using revolutionary swimsuits. To highlight the issue, note that it is rare to break world records, but in 2008, 70 world records were broken in one year, and 66 Olympic records were broken in one Olympic Games (there were races in Beijing where the first five finishers were swimming faster than the old world record). Despite many of his records having been won in these suits, Michael Phelps stated that he might boycott the competition after his record was beaten by another swimmer with a more advanced suit.
As of New Year's Day 2010, men are only allowed to wear suits from the waist to above the knees.They are also only permitted to wear one piece of swimwear; they cannot wear speedos underneath jammers. This rule was enacted after the controversy in the Beijing Olympics and Rome World Championships.

Women

Swimming at the 2008 Summer Paralympics.

Women wear one-piece suits with different backs for competition, though there are two-piece suits that can be worn to compete as well. Backs vary mainly in strap thickness and geometric design. Most common styles include: racerback, axel back, corset, diamondback, and butterfly-back/Fly-Back. There are also different style lengths: three-quarter length (reaches the knees), regular length (shoulders to hips), and bikini style (two-piece). Also as of New Year's 2010, in competition, women are only allowed to wear suits that do not go past the knees or shoulders.

Use of drag

Drag suits, used by women, and drag shorts, used by men, are used for increasing the resistance against the swimmer in order to help adjust the swimmer to drag. They are not worn during competitions. Instead, when swimmers switch back to normal practice suits they swim faster as a result of feeling less resistance. Other forms of drag wear include nylons, old suits, and T-shirts; the point is to increase friction in the water to build strength during training, and increase speed once drag items are removed for competition.
Some swimmers also shave areas of exposed skin before end-of-season competitions to reduce friction in the water. The practice gained popularity after the 1956 Olympics, when Murray Rose and Jon Henricks came shaved and won gold medals for Australia. Freshly shaven skin feels much smoother and less resistant in comparison when in the water. In addition, a 1989 study demonstrated that shaving improves a swimmer’s overall performance by reducing drag.
The mental aspect of wearing drag is critical because the goal is to feel your best in the water on race day. Drag makes a swimmer feel slower and more resistant during training with the added friction. Then on the day of the competition, a shaven swimmer wearing only a fast competition suit will feel a drastic and noticeable improvement in how fast and smooth they feel in the water. As in every other sport, mental training is just as important as physical training.