Zip Fin Swim Fins are ideal for building knee strength after knee surgery or getting a maximum full-leg workout. Zip through the water less ankle fatigue with Aqua Sphere Zip Fitness fins.

Want to swim like Michael Phelps but you lack size 14 feet with double jointed ankles?

Swim fins give you that fluid motion of speed. And most of us are not born with a swimmer's body as natural to the sport as Michael Phelps. But swim fins can deliver that pseudo Phelps feeling and give you a great leg workout in the process.

Technical Jargon from the Manufacturer

OK, you sports scientists out there here are the engineering aspects of these fins and how they work:

The fin's specially designed split blades twist independently during each stroke, reducing turbulence around the blade. Specially engineered side rails, strategically aligned flex channels, and stiffening battons on each blade ensures proper angle of attack for top lift and thrust. Open heel foot pocket features a soft neoprene ankle strap with an easy-adjust buckle system. Comfortable foot pocket offers open heel/open toe design.

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Ideal workout assistant for hurt knees

These are engineered to offer a maximum leg workout without putting joints in peril. If your knees are about to give out or you've had knee surgery, these will build or maintain leg strength and offer an alternative to exercise which puts too much pressure on the knees and ankles from sports like running.They are adjustable and very comfortable while being efficient and pretty darn exhilarating since you cut through the water at blazing speed.

Some Triathletes like these for Building Leg Endurance and Muscle While Training.

Triathletes have told me that these are great for the ocean in preparation for an event. The ones whom I interviewed that use them do not use them every time out since they can't be used in a race, but they use them to build leg strength.

From a safety standpoint they provide extra insurance for ocean swimming since the tide can literally turn on you in minutes from calm to rough rip tides. When the sea is rough, it's hard to get anywhere and these offer some insurance that you will if waters get rough.