An aquatic exercise device which is to be used within a body of water such as a pool has an element which can be engaged by the foot or hand of an individual, which element is linked to a piston-cylinder combination so that as the user engagement element is moved by the user the piston rides in the cylinder....http://www.google.com.tw/patents/US5868649?utm_source=gb-gplus-share專利 US5868649 - Aquatic exercise device
