Existing research points to sex-specific biological and physiological differences, but the effects of sex and age on water polo-specific motor skills have not yet been sufficiently investigated. The current study investigated sex- and age-related disparities in in-water vertical jump, change of direction ability, sprint performance, aerobic fitness and shot velocity, hypothesising that these variables are related to the players’ specific motor performance. Sixty-six players (47 males, 19 females) were split into an adult and a young group (each with n = 33). Two-way (sex and age as factors) analysis of variance and Tukey’s post hoc test were employed to evaluate the influence of sex and age on specific water polo skill performance. The male players’ in-water vertical jump (135.4 ± 8.1 vs. 121.5 ± 6.1 cm), shot velocity with previous displacement (68.3 ± 6.4 vs. 51.0 ± 2.5 km·h⁻¹) and without displacement (68.5 ± 5.7 vs. 52.2 ± 2.9 km·h⁻¹), 10 m sprint (5.6 ± 0.9 vs. 6.6 ± 0.4 s), aerobic fitness (311.7 ± 92.1 vs. 235.7 ± 70.3 m) and change of direction (3.3 ± 0.4 vs. 3.9 ± 0.4 s) scores were superior to those of female players. No significant age-related differences were observed in shot velocity with previous displacement (F (1,53) = 2.124, p = 0.151, η²p = 0.039) or 10 m sprint performances (F(1,62) = 0.935, p = 0.337, η²p = 0.015). Male players outperformed females in most water polo-specific motor skills, while age-related differences were limited.