Recreational diving is still a relatively young sport. Created in the 1950s, it gained acceptance in the '60s and '70s, boomed in the '80s and grew by great leaps in the '90s. If you've been diving for decades, there's a good chance that not everything you learned in your open-water class still applies. New research and equipment have made diving safer and more enjoyable than ever - if you know the rules.

We decided to take a look at some of them and see how they've evolved.