Just wanted to add what
Suunto has to say about the use of the Harte Rate monitor 'under' water:
Measuring heart rate under water is difficult of two reasons: - Highly chlorinated pool water and sea water can cause a short circuit in the electrodes, which makes detecting heart rate impossible. - In water activities the transmitter belt easily moves from its correct position. Even though
Suunto Wristop Computers are watertight to a certain depth depending on the product, they are not intended to diving or other underwater operating.