The purpose of the present study was to determine the physiological and technical differences between the use of wetsuit compared with the swimsuit in two specific environments the 25m swimming pool and a swimming flume. A total of 33 triathletes and open water swimmers (age 26.46±11.72 years) participated in the study. The trials were made with and without full body wetsuit randomly and counter balanced for each experimental condition. Two 400m trials were randomly performed in a 25m pool, one wearing wetsuit and another wearing training swimsuit. Two mores trials performed in the swimming flume with the same duration than the swimming pool trial at the same mean water velocity. The analysis carried out was the repeated measurement ANOVA to determine the differences between four experimental conditions. The results revealed the four experimental conditions had a main effect on velocity (F 3,96 = 114.02 P<0.