SDI Open Water exam with correct solutions

What is the absolute pressure (in atm) at 66 feet? 2 atm What will be the volume in a ball that is filled with two cubic feet of air at 99 feet when it's taken to the surface? 8 cubic feet How many more times dense is the air in a balloon at 4 atm compared to the air density at the surface? 4 X as dense What is the abbreviation for an atmosphere? atm If a scuba cylindar lasts 2 hours (120 minutes) at sea level, how long will it last at 66 feet? 40 minutes How often should a diver equalize during a descent? Early and often What should you do if you experience discomfort in your ears while descending? Stop descent, ascend a few feet. Equalize, then descend again. What is a reverse block? Pressure caused by air spaces in your body expanding during ascent. What is squeeze? The painful compression of air spaces in your body or equipment during descent. What should you do if you experience a reverse block upon ascending? Descend a few feet until the pain subsides. Wait a few moments. Then, ascend again.