As white light travels through water it is not only refracted and scattered, it is absorbed or 'attenuated' by the water. Varying wavelengths, or colours, are absorbed at differing depths; organic matter also adding to this absoption.

These are my presentation notes from the Maxwell City workshop in June this year.

Extremely low frequency transmitters were developed for communication with deeply submerged submarines at depths of more than 200 metres and under polar ice-caps. Submarines below this depth are undetectable by radar and other non-acoustic systems.

This link is for a first stage edit of Underwater Tea Table and at the moment there is no added audio.