30 feet under water, your body begins to transform back into its original form, so the blood starts to turn green. It's why we weren't allowed to breathe underwater. Our true nature would come out if we stayed there too long.
And no kniggity it's around 20-30 feet. Low frequency radiation is filtered out real fast by water (and most other things). IIRC green is around 100 feet.
ftfy.
Love a fellow diver.
P.S try cracking an egg at 100 ft, the pressure keeps the yolk and fluids in tact and you can play yolk ball xD