I really enjoy going SCUBA diving with my spouse. It is so much fun to be able to breathe underwater and explore. 
It sounds really fun. But I've always wondered. what does scuba stand for?
SCUBA stands for Self-Contained Underwater Breathing Apparatus. People usually take compressed gas with them. 
I think I learned that from boy meets world, but forgot. Haha.
That was a great show! When you are SCUBA diving, an open circuit system lets the breathing gas go into the environment as you breathe out. It's a fascinating system.  
How long can a person stay under water when diving?
It really depends on a lot of factors like how much air is in your tank as well as how deep you go. For instance, you may run out in an hour or less time if you dive deeper. You need to learn a lot of skills before you go. 
Wow, the fact that it can even last an hour is kind of impressive.