Swimming is one of the team sports that provides a way for health and better quality of life. However, few studies are commonly reported in young Latin American athletes, in which the knowledge is addressed to the structure and function of the human body in relation to athletic performance. This study comprises the pilot sample of 41 male and female young swimmers at competitive levels. Age ranged between 9 to 17 years of age. The aim was to explore anthropometric variables (weight, height and sum of 8 skinfolds) and water physical fitness test (sprint and long distance events) according to stage of maturation. Descriptive analysis included box-plot diagrams to look for dispersion of variables and Student t test to study sexual dimorphism. Groups were partitioned into categories of prepuberty, initial puberty (stages 2 and 3) and late puberty (stages 4 and 5), according to Tanner-Marshall method. Skeletal maturation was assessed with Tanner- Whitehouse (TW2) method. Results showed that girls were only taller and heavier than boys at the initial stage of maturation, with a higher sum of skinfolds values in all groups. In boys at the late stage of puberty, skeletal maturation was more advanced than chronological age in almost 1.5 years differences between ages. Very low differences were attained for boys and girls in short and middle distance events at the prepubescent stage. At the onset of puberty the differences are marked only for middle distance events that favors boys. At late puberty boys perform better than girls in short distance, whilst girls do better in middle to long distance events.