Comment by trhway

i'd guess it is faster than the physically the same, just 90 degree rotated, dolphin kick only because of the proximity to the surface - in the dolphin kick significant energy gets wasted as the surface wave (i.e. instead of pushing yourself from the large mass of water, you push the smaller amount of water above you into a surface wave, the same reason you want your boat prop to be as deep as possible). My bet would be that the fish and dolphin kicks would give the same performance if both performed at sufficient depth, like 5-10 meters.