Background: The “athlete’s heart” has been well characterized, and it is known that remodeling is dependent on the nature of the hemodynamic-stimuli. Aquatic-athletes are exposed to hydrostatic pressures, postural anomalies, and breath-holds that likely drive distinct cardiac adaptation; however, the aquatic-athlete’s heart has not been specifically interrogated. The aim of this investigation was to characterize and compare the sport-specific cardiac structure of elite aquatic-athletes. Methods: Ninety athletes at the 2019 FINA World Championships from swimming (SW:20M/17F), water-polo (WP:21M/9F), and artistic swimming (AS:23F) volunteered for echocardiographic assessment of cardiac structure. Results: Male SW displayed primarily eccentric volume-driven remodeling, while male WP had a greater incidence of pressure-driven concentric geometry (SW:5%, WP:25%) with elevated relative wall-thickness (RWT) (SW:0.35±0.04, WP:0.44±0.08, P<0.001). Female SW and WP hearts were similar with primarily eccentric-remodeling, but SW and WP had greater concentricity index than artistic swimmers (SW:6.74±1.45g/(ml)2/3, WP:6.80±1.24g/(ml)2/3, AS:5.52±1.08g/(ml)2/3, P=0.007). AS had normal geometry, but with increased posterior-wall specific RWT (SW:0.32±0.05, AS:0.42±0.11, P=0.004) and greater left atrial area than SW (SW:9.7±0.9cm2/m2, AS:11.0±1.1cm2/m2, P=0.003). All females had greater incidence of wall-thickness ≥11mm than typically reported (SW:24%, WP:11%, AS:17%). Conclusion: Male athletes presented classic sport-specific differentiation, with SW demonstrating primarily volume-driven eccentric remodelling, and WP with greater concentric geometry indicative of pressure-driven remodeling. Female SW and WP did not display this divergence, likely due to sex-differences in adaptation. AS had unique LV-specific adaptations suggesting elevated pressure under low-volume conditions. The overall incidence of elevated wall-thickness in female athletes may point to an aquatic-specific pressure stress.