Swim Like a Monkey

In this first video, the monkey has very little wasted motion and there appears to be very little energy expended. Now check out this video of Alexander Popov, perhaps the most efficient sprinter the world has ever seen:

Popov clearly has tremendous hip and shoulder rotation, and though the video is in slow motion, he shows incredible fluidity of movement. He has very little wasted motion and when racing appeared to barely be trying.

This swinging "monkey bar" action looks a lot like swimming freestyle if you turn it on its side. As the monkey anchors his hand on the bar, Popov anchors his foreharm and hand in the water. As the monkey turns his hips and shoulders and trades gravity for forward momentum, Popov rotates his hips and shoulders and trades gravity (from one hip being elevated) for leverage on his forearm anchors. Whereas the constant force for the monkey is gravity, this constant force for Popov is his legendary kick.
So to swim with fluid efficiency of a swinging monkey like Alexander Popov it is vital that one use 1) a high elbow catch to establish a solid anchor, 2) a fluid, connected rotation of the core to get from one stroke to another with maximum length and leverage, and 3) a powerful kick.