Fish swimming closer to the surface had the highest rate of injury or mortality. Let's explore why.

When TDG is at 110% at the surface of a water body, the TDG saturation one meter (3 feet) below the surface is 100%. For each meter you go down in the water, because the water pressure goes up, the TDG saturation actually experienced by the fish drops by 10%. So when the surface TDG is 120%, a fish two meters down is exposed to a TDG level of only 100%.