Divers are influenced in their performance by various factors. The aim of this study was to conduct a performance test to determine the impact of thermal protection suits on the load experienced while diving with a compressed air diving apparatus. A three-stage stress test with diving speeds of 0.4, 0.6, and 0.8 m/s, as well as a maximum speed test, were used as performance diagnostic methods. Based on the parameters of heart rate, perceived exertion (RPE), and maximum speed, and their changes when using wet suits, conclusions were to be drawn about the differences in exertion during underwater movement. Additionally, the influence of the environment, comparing indoor pools to open water, was to be examined. The study aimed to answer whether heart rates during the pre-test phase differed among the various conditions.