This study aimed (1) to analyze the development in squat jump height and swimming start performance following an altitude training camp, (2) to correlate jump height and swimming start performance before and after the altitude training period, and (3) to correlate the percent change in squat jump height with the percent change in swimming start performance. Fifteen elite male swimmers from the Spanish Junior National Team (17.1 ± 0.8 years) were tested before and after a 17-day training camp at moderate altitude. The height reached in the squat jump exercise with additional loads of 0%, 25%, 50%, 75%, and 100% of swimmers' pretest body weight and swimming start performance (time to 5, 10, and 15 meters) were the dependent variables analyzed. Significant increases in jump height (P < 0.05; ES: 0.35-0.48) and swimming start performance (P < 0.01; ES: 0.48-0.52) after the training period were observed. Start time had similar correlations with jump height before training (r = -0.56 to -0.77) to after training (r = -0.50 to -0.71). The change in squat jump height was inversely correlated with the change in start time at 5 meters (r = -0.47), 10 meters (r = -0.73), and 15 meters (r = -0.62). These results suggest that altitude training can be suitable to enhance explosive performance. The correlations obtained between the squat jump height and the start time in the raw and change scores confirm the relevance of possessing high levels of lower-body muscular power to optimize swimming start performance.