I wonder if you could use free space optics or mm wave radio (above the absorption spectrum of water) to do this without the environmental externalities. Dispe

I wonder if you could use free space optics or mm wave radio (above the absorption spectrum of water) to do this without the environmental externalities. Dispersion is still a problem underwater with these high frequency EM waves, but presumably a researcher could deploy some relays along with the cameras. Passive sound absorption for power could also work without any sort of active sonar pinging.