Four of the most popular modes of aquatic exercise are deep water (DW) exercise, shallow water (SW) exercise, water calisthenics (WC), and underwater treadmill (UT) exercise. The mechanical requirements of each aquatic exercise mode may elicit different physiological and biomechanical responses. The purpose of this descriptive literature review was to evaluate some biophysical differences between aquatic and land-based exercises. The biophysical variables reviewed included oxygen consumption (VO2), heart rate (HR), rating of perceived exertion (RPE), stride length, stride frequency, pain, and measures of functional gain. Based on the studies reviewed, when compared with similar land-based exercises, VO2 and HR maximum values were lower during DW and SW exercise, but, depending on water depth and exercise performed, may be greater during WC and UT exercise. RPE during DW exercise was generally similar to land exercise during max effort. Stride frequency tended to be lower for all four aquatic exercises, relative to onland counterparts. Pain levels tended to be similar between WC and land exercise, yet may decrease after UT exercise.