In many applications the study of human movement using a computer vision and graphics techniques is very useful. One of these applications is the three-dimensional reconstruction of the structure of the human body and its movement using sequences of images and biomechanical graphics models. We present a whole and general system to study the human motion without markers but, in this case, we apply it to high-level competition disabled swimmers. This kind of study needs accuracy on the analysis and reconstruction of the person's body, therefore the virtual human (avatar) must have similar anthropometrical characteristics than the person who is doing the movement. We define a process to adjust the humanoid to the morphology of the person. It could be very laborious and subjective if done manually or by selection of points, but in this article we present a global human motion system capturing, modeling and matching a semiautomatic process between the real person and the modeled humanoid or synthetic avatar. Semiautomatic means that the computers propose the best matching from previous frames and the user can accept it or not. Once this process is carried out we are ready to analyze and represent the movements under study. It must be defined a specific set of parameter for every kind of sport. The study is adapted to specific sport activities, in our case swimming activities with an additional complexity: water occlusion and distortion. In these cases the adjustment process must be assisted by the computer using rules and models to help the expert user in correspondence tasks.