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 reccommend deep submersion with the device. Please note that MZ-1 belts are not water resistant nor are they waterproof.
If you decide to swim with your MZ-3, it will be safe up to 10 meters. However, moving through the water creates drag between the strap and skin therefore negatively impacting the accuracy of the heart rate readings which is why we do not classify them as a "swimmable" device.
Some users have reported accurate readings wearing the belt underneath a wetsuit to keep the black pads in contact with their skin. However, others have reported receiving inaccurate readings or no results at all even wearing a wetsuit so we cannot make any guarantees about HR accuracy while swimming in the pool.
Keep MEPing it dry, folks!