How Important is Gravity?

I've been writing about what I'm calling the movements of evolution.
This started when I noticed that my dog Jake has a "fish" walk, not a trot just a walk. This journey was also sparked by my reading Serge Gracovetsky's book, "The Spinal Engine" that premises that bipedal locomotion starts in the spine and not the legs.
I took Jake swimming the other day--actually he swims a lot but I noticed something the other day--and noticed that his swim gait is a walk, not a trot, and that while he was swimming or walking in water--not on--his pelvis movement was that of a mammal and not a fish! Can we postulate that water removes the effects of gravity? If so than we can also postulate that whatever causes him to walk like a fish is dependent on gravity.
More thought is needed.
I'm working on animations of the different pelvis movements and will post them to the website when they're done.