A fin assembly for aqua resistance exercise comprises a strap having an inner strap and an outer strap, and with fastener(s) provided to an outside of the inner strap and an inside of the outer strap to releasably attach the inner and outer straps together. One or more fins are received on the outer strap and a longitudinal position of the one or more fins is secured by engagement of the inner strap to the outer strap. The length of the inner strap is longer than a length of the outer strap, so that an extending end portion of the outer strap can overlap and engage an opposite end of the outer strap to secure the fin assembly about the user's limb.