For a swimmer, to enhance his/her swimming abilities, it is desirable for swimmers and/or coaches to understand and evaluate the characteristics of own swimming motions, such as strokes and turns etc. One useful method is to use a motion capture device. However, its device requires the high cost and complicated setup. On the other hand, the wearable sensors do not require them. For these reasons, we plan to develop a system to evaluate the characteristc of the swimming motions with a single underwater wireless wearable sensor. This system gives assistant information to swimmers and/or coaches. In this paper, we discuss the framework and requirements of the system.
