Underwater capabilities of Apple Watch

Locked is not a problem for passcode lock, but answering a call while the screen is locked by Water Lock could be rather more difficult. Being under water is probably a showstopper because the radio signals will be attenuated and may be too weak to be usable - but this will depend on the strength of signal above the water, and also the depth under water (deeper will be weaker). Then there’s another problem... how do you hear and talk to the watch while under water?