Here are the latest implications of the value of bodysuits for competitive swimmers. Breaststrokers should never wear them. Crawl stroke swimmers can wear them but not beyond 200 m. Butterfly swimmers can wear them, but should think very carefully about using them for a 200m race. Medley swimmers should never wear them for any distance.
Any suit only provides floatation, and therefore performance, benefits when they are worn dry.
A tight bodysuit will interfere with dives and turns by inhibiting hip and knee flexion. A tight bodysuit on the torso will reduce muscle and joint efficiency and interfere with stroke movements. No arm or lower leg covering should be used. Science has shown that bodysuits only add to performance improvements in the above conditions for unshaven swimmers in training suits. Bodysuits provide no benefit to swimmers who are shaved and wearing tight traditional suits.