Why is a diving limit set for scuba diving?

Answer 1

For humans, the intense increasing in pressure at great depths would be fatal.

Some fish cannot live at depths for this reason as well, but aslo due to the low oxygen concentrations.

ANS2:A sport diver is limited to 130 feet because at that depth the partial pressure of oxygen in compressed air is 100% and oxygen toxicity would be a problem. Mixed-gas divers (professional divers) can go deeper because they use mixtures of gases that minimize the effects of both oxygen toxicity and nitrogen narcosis.

The link claims that a 3-gas mix allowed diving to a depth of 2132 feet.

Answer 2

How long can you hold your breath? That's how deep you can go.

Pushing limits while free diving poses risks such as passing out. However because you are not taking in compressed air while below the surface you do not risk decompression sickness or lung over expansion.

Answer 3

For recreational divers, the deepest limit of 130 feet (40 meters) is set due to narcosis primarily and breathing gas restraints secondarily.