Don't buy this if your intention is to keep track of calories burned while swimming or doing water aerobics or other wet exercise. Even though this watch/heart rate monitor is advertised as being "water resistant" -- the heart rate monitor does not work if it is wet, or if your fingers are wet. Mine gives totally wacky reading for my heart rate if I'm swimming. Sometimes, if I take the time to dry off my fingers and the buttons, I can get a reasonably accurate reading for my heart rate, but by then, my heart rate has returned to it's resting level which, isn't the number I'm interested in obtaining. Monitor seems to work fine if it's totally dry, but I usually get my exercise by swimming. I think it was a waste of money for me.