Perfect buoyancy for tall, heavy boned, low fat swimmers. I watch my wife swim with envy. The top of her butt is floating level with the water surface and she is not even kicking! I, on the other hand, have to kick constantly to keep on plane. Thanks to these pants I can vary my kick beats and even go down to 2 beat kick and stay on plane. My arm reach is 6" longer than my height (ape index 1.09) and these pants allow me to take less strokes (17-19/25m) but with a little more power due to buoyancy. I use way less energy when I am cruising on a 2K plus day. I do not compete and never intend to, but I do swim 5 days a week and one day in the ocean just for a change of scenery and the rush. That said, these pants add additional speed in the ocean but more importantly they add safety. If your leg cramps you will be able to float on your back and relax or just swim to the shore without kicking. Please note: I did try ROKA buoyancy pants but they were Mediums and my CORE pants are XL which may have been a reason they were not as buoyant. The ROKA's consistency averaged about one stroke longer per 25 meters. Hope this helps!