Control of massive hemorrhage (MH) is a life-saving intervention. The use of tourniquets has been studied in prehospital and battlefield settings but not in aquatic environments. The aim of this research is to assess the control of MH in an aquatic environment by analyzing the usability of two tourniquet models with different adjustment mechanisms: windlass rod versus ratchet. A pilot simulation study was conducted using a randomized crossover design to assess the control of MH resulting from an upper extremity arterial perforation in an aquatic setting. A sample of 24 trained lifeguards performed two randomized tests: one using a windlass-based Combat Application Tourniquet 7 Gen (T-CAT) and the other using a ratchet-based OMNA Marine Tourniquet (T-OMNA) specifically designed for aquatic use on a training arm for hemorrhage control. The tests were conducted after swimming an approximate distance of 100 meters and the tourniquets were applied while in the water. The following parameters were recorded: time of rescue (rescue phases and tourniquet application), perceived fatigue, and technical actions related to tourniquet skills. With the T-OMNA, 46% of the lifeguards successfully stopped the MH compared to 21% with the T-CAT (P = .015). The approach swim time was 135 seconds with the T-OMNA and 131 seconds with the T-CAT (P = .42). The total time (swim time plus tourniquet placement) was 174 seconds with the T-OMNA and 177 seconds with the T-CAT (P = .55). The adjustment time (from securing the Velcro to completing the manipulation of the windlass or ratchet) for the T-OMNA was faster than with the T-CAT (six seconds versus 19 seconds; P < .001; effect size ES = 0.83). The perceived fatigue was high, with a score of seven out of ten in both tests (P = .46). Lifeguards in this study demonstrated the ability to use both tourniquets during aquatic rescues under conditions of fatigue. The tourniquet with the ratcheting-fixation system controlled hemorrhage in less time than the windlass rod-based tourniquet, although achieving complete bleeding control had a low success rate.