Many beach resorts offer a few hours of scuba training, then a dive, which may seem like going from a crawl to a run. That being said, that doesn't mean that it isn't safe. 

Ultimately, the safety of the course-then-dive offered at a resort depends on the quality of instruction and your comfort level with being underwater. Daylong resort intro courses don’t provide actual certification, just enough know-how to try things out, says Alex Brylske, Ph.D., author of The Complete Diver. Group dives are limited to a max depth of 40 feet and avoid “overhead environments,” like caves or shipwrecks. And the next vacation, you have to take the class all over again.

“Some people have great experiences” with starter-type classes, Brylske says. But currents and visibility can create danger, and shoddy operators are a risk. So if you go this route, ask if your outfitter follows Recreational Scuba Training Council (RSTC) rules.

A much better idea? Get your “C card” (open-water certification) before you go. “A typical course takes about 30 hours over six to 10 weeks, starting in a pool then moving to open-water dives,” says PA-based diving teacher Brett Galambos.

Sound like a lot of work? Consider the reward: a lifetime of diving reefs in Bonaire and shipwrecks off the Florida Keys.