The substitution of the battery of the Mares Smart Apnea is easy and can be done by anybody, being though careful in following some shrewdness.
Making a mistake in changing the battery can determine a big damage to the wrist computer. Mares communicates that the substitution of the battery can be done by the owner of the watch, but warranty ends in case of water infiltrating in the watch. Mares suggests buying the high quality battery plus o-ring (circular gasket that insures watertight sealing) kit.
Below the tutorial for the substitution of the battery on the Mares Smart Apnea.