The aim of the present study was to assess the kinematical changes when swimming maximal bouts in Front Crawl and Breaststroke with the AquaTrainer snorkel. Thirteen male swimmers (7 at Breaststroke and 6 at Front Crawl) of national level performed randomly two maximal bouts of 100-m swims: one bout using the AquaTrainer snorkel (snorkel swim) and another one without the snorkel (free swim). The swims were videotaped in sagittal plane with a pair of cameras providing 2D kinematics evaluation. The following measures were assessed: swimming performance (T100), stroke cycle period (P), stroke rate (SR), stroke length (SL), swimming velocity (v), swimming efficiency as estimated by the stroke index (SI), speed fluctuation (dv) and the mathematical characterisation of dv. T100 was significantly higher when swimming with the snorkel than in free swimming at Breaststroke (Delta = 6.26%) and at Front Crawl (Delta = 4.75%). P, SR and SL, as well as SI and dv did not present significant differences. The main finding of the study was that changes in the swimming velocity imposed by the use of the Aquatrainer do not seem due to changes in general kinematics or swimming efficiency.