In scuba diving. what does 33ft signify?

Question

In scuba diving. what does 33ft signify?

Answer 1

33' is one atmosphere at sea level.  

Also, if I'm remembering correctly, at one atmosphere - breathing pure oxygen would be fatal.

Answer 2

33 feet (10 meters) is the point also where nitrogen absorption starts to become an issue. Very long bottom times are allowed at 30 feet and shallower per the tables, and they become shorter as you go 40 feet and deeper. Most computers are more conservative.

Answer 3

your gonna die

Answer 4

Every 33 feet exerts another ATM