At what depth are decompression stops required?
The deeper and longer your dive the more chance you need decompression stops. Shallow dives of 6-10 metres (20-30 feet) you can spend over 200 minutes without a decompression stop. Dives to over 30 metres (100 feet) limit your dive time to around 20 minutes before a decompression stop is required.
How much pressure can humans survive?
Air presses down on you at all times at 14.5 pounds per square inch, also called one bar or one atmosphere. Human beings can withstand 3 to 4 atmospheres of pressure, or 43.5 to 58 psi.