I live in South Florida and I’ve Snorkeled a few times before and it’s a lot of fun. I’m thinking about going into SCUBA diving, but I hear it’s very expensive (certification, buying the gear, chartering boats, etc). Is it worth it?

Scuba. Snorkeling just doesn’t cut it for me. Why don’t you head to your local PADI dive shop and sign up for a Discover Scuba course. It’s free and will get you in a pool with basic instruction and supervision for an hour. If you like it, take it from there. The Open water cert, costs anywhere from 250 – 350 dollars, depending on who you take it from. You really only need personal gear to start, whcih is the same as snorkeling. Mask, fins and snorkel. The rest, once you have your Open water cert, you can rent anywhere in the world.
As for dive charters, they can actually be pretty cheap. They average about 50 bucks for a two tank dive but in some locations, can be upwards of 90 bucks.
Is it worth it? Yep, I doubt you’ll ever go in without a tank again. How many snorkelers get to explore wrecks, reef canyons or play with an octopus for more than the time you hold your breath?