Is there any difference in knee angle when finning?

[Progen]

The classic example of a diver in good trim seems to be flat with the knees at 90 degrees or close. Mine are pretty far from 90. I assume that with the knees at 90, the diver will have more pushing power when doing a full frog kick as he / she extends her legs but are there any other differences?

 

[Progen]

It's been a while but to answer my own question after some observations, when the knees are close to 90 degrees and now that I've gotten more flexibility in the ankles from regular diving (and perhaps some running), although there's less overall movement in the legs, the short ankle flicks with most of the upper and lower legs stationary seem to give just as much thrust as pushing with the feet and lower legs.