Underwater Transmission Possible

This is some really interesting technology. I've worked in radio for a while and water is a true enemy. Trying to get certain frequencies through a tree full of water filled leaves is sometimes impossible. However it is pretty transparent to low frequencies and long wavelengths.

www.theengineer.co.uk...
When wireless communication is transmitted through the air by systems like Bluetooth, there are significantly fewer technical obstacles to overcome. But in seawater there is limited bandwidth available and signals are subject to signal interference. In shallow water, signals bounce from the surface and sea bed, while in deep water, acoustic waves tend to travel in the depth of water where sound moves the slowest. The scattered movement of these waves creates signal echoes, which create interference in a digital communication system.

Data rates presently are 8kbps over 60km at frequencies down to 5khz. Impressive considering it's through water.

Lightning is the main natural source for these frequencies on Earth. Because of this I'm a bit concerned for some forms of sea life. Some types of sonar cause animals to literally leap out of the water or even suffer internal bleeding and death. To them, the sonar is fatally loud. To other animals could this be fatally bright?