from what I know most of the polar ones are rated for "water resistance", such as swimming etc. I wear mine regularly, and no one knows I am wearing it, unless I take my shirt off to swim. But even when I swim in the surf I have a thin wetsuit and wear it under my setsuity and no one knows, there are no wires between chest strap and "wrist watch" receiver. The chest strap has a couople of areas that sense the hearts electrical activitry through the skin, and a small, battery powered transmitter that clips to the chest strap. Your watch and transmitter are coded to each other. If you are after a heartrate monitor, just get a polar one. Ring them and have a chat to tak about what sort to ge, what is the current version of the RS100, and depending on how much you can spend, but it will all become clear one you get one....honestly, just get one, they are very useful if you want o monitor your hear rate while exercising and walking or anything. I eally enjoy using mine.