I have done it quite a few times, mainly because I was unlucky with the law. When I was 12 years old I spent a few months training and learning, I took my test and passed and was given my license. About a month later my license was revoked, the law changed and now you needed to be 16 years old to scuba dive. I waited patiently and the same thing happened, except this time after I got my license it was changed to 18.
I finally got my license at age 18, and started going on dives. When you learn it is always in shallow water or swimming pools, so it was a fair time until I went on my first dive.
The experience was great, and I can’t recommend it enough. It totally changes your mind of what the ocean is like, almost like opening up a new world.
Advice, be very careful. It is very dangerous and there is more than one way of killing your self. The man who instructed me and helped me get my license ended up dead. He went down alone to explore a shipwreck and never came back up.
Learn about: currents, things you can get stuck in, poisonous things, nitrogen in the blood and the bends, temperature, and be generally cautious.
Make sure you learn properly and have all the permissions you need, there is lots of information to learn, including special sign language and a whole lot more.