You can swim with the MZ-Switch with the wrist band only. Do not swim with the MZ-3 or MZ-1.
MZ-Switch
If you own an MZ-Switch, it is perfectly safe to swim with your Switch on your wrist only! The wrist is the only location that will pick up MEPs and accurate data while in the water. Please do not wear your MZ-Switch on your chest or forearm when swimming.
MZ-3 & MZ-1
While the MZ-3 belts themselves are water-resistant, they are not necessarily waterproof. This means that you can take the belt into the pool without risk to the device itself, but we do not recommend deep submersion with the device. Please note that MZ-1 belts are not water-resistant nor are they waterproof.
Your MZ-3 is safe up to 10 meters. However, moving through the water creates drag on the strap, pulling it away from the skin and causing it to disconnect. Some movers have reported accurate readings wearing the belt underneath a wetsuit to keep the black ECG sensors in contact with their skin. However, others have reported receiving inaccurate readings or no results at all even wearing a wetsuit. For this reason, we cannot make any guarantees about HR accuracy while swimming with the MZ-3.