Finnish free diver Johanna Nordblad explored an underwater world beneath the ice under cloudy skies (mimics red light days) to help heal her tremendously damaged leg. She found that the isolation the water brought to her the better her leg got.
This experience mimics what we find in modern man-made isolation tanks.
Johanna used cold free diving to restore health in her bad leg. She got the message from nature that restoration of her free radical signaling in her damaged leg was the key mode in her recovery.