Morphology of swimmer and fluid dynamics
Swimming is a complex sport. It requires special physical qualities because they are not natural for the land bipeds we are. Indeed, contrary to many other sports, the arms do the main part of the movement (70% of the power). The biggest muscles of our body (thighs) are little used. Furthermore, water is a viscous fluid which requires an excellent technique to minimize the friction.
The swimmers have very different morphologies depending on each stroke (breast, butterfly, freestyle, etc.) as well as the distance (a short-distance swimmer does not look like to a long-distance one).
Even if this situation is common to other sports (running, cycling, etc.), in swimming it takes a huge importance. A swimmer should adapt his technique to his morphology and will be able to compensate in glide his lack of power.
The two main dynamics phenomena to consider for a movement in the water are the viscous resistance and the front wave resistance.
The viscous resistance is the most important phenomenon. It depends on the water viscosity which generates a friction. The "pull-push" chains allow decreasing this resistance from a perfect synchronism.
The front wave resistance is a phenomenon coming from the head and the shoulders as for a boat stem which generates a wave which opposes to the movement. The position of the body is fundamental to limit this resistance.
All these things prove for example, that for the Rome OG, the 100 m was in 52 s with 52 arm knocks while for the Sydney OG, it was 47,8 s with 45 arm knocks.
C.B & J.L