The purpose of the study was to compare the effectiveness of an aquatic- and landbasedplyometric programme upon selected, sport-specific performance variables inadolescent male, rugby union players.A group of 52 rugby players (age: 16.3 ± 0.8 years, height: 176 ± 6.9 cm and bodymass: 76.1 ± 11.9 kg) were randomly assigned to one of three groups: aquatic-group(n=18), land-group (n=17), and a control-group (n=17). Prior to and after the sevenweeksof training, the power, agility and speed of participants were assessed bymeans of Fitrodyne repeated countermovement jumps, the Sergeant vertical jump,the Illinois agility test, a standing broad jump, and a 10- and 40- metre sprint. All threegroups maintained their summer extra-curricular sport commitments during theintervention period.When the three groups were analysed, no significant differences were found betweenthe groups with regard to all tested performance variables. With regard to withingroupchanges, the aquatic-group improved significantly (p<0.05) in the Illinois agilitytest, performed to the right. The land-group showed significant (p<0.05)improvements in peak concentric power during Fitrodyne repeated countermovementjumps. All groups reflected highly significant (p<0.01) improvements in the Sergeantvertical jump. None of the groups displayed any improvements in sprint speed. Thecontrol was the only group to improve significantly in the standing broad jump(p<0.05).Land-based plyometric training might be a functionally superior training modality forathletes, although aquatic plyometrics could also offer an effective training modalityfor performance enhancement in power-based sports such as rugby union football.Aquatic-based plyometrics should not completely replace land-based plyometrics, asit might not adequately develop the specific neuromuscular patterns or functionalneeds of explosive sports.