As he demonstrates the swimming behavior of robots, made from Tupperware and simple circuits, in the large pool in his laboratory at Vassar College in Poughkeepsie, New York, he almost seems to float a few inches off the floor. (sciencemag.org)
Keeping core tight, slowly extend legs, allowing them to hover a few inches off floor (raise them a bit higher if that's too challenging), and lean back until your mid-back almost touches floor. (health.com)
Slowly bend elbows, lowering body until you're hovering a few inches off the floor; keep back flat, elbows close to sides and head in line with body. (health.com)