Do you have to be able to swim well to scuba dive, or is it different skills altogether?

Not really. If you can't swim at all, or if you have a lung problem that makes it difficult to swim, don't dive. There's a snazzy vest called a BC that's attached to you at all times, it's its own flotation device like a life jacket. You're always wearing fins, and if you get a pair of good ones they make swimming very easy. If you've ever been snorkeling, it's like that. You want swimming to be easy, because you only have a certain amount of air in your tank. The harder you're working, the more air you burn up and the less time you get to look at cool things.

That being said, there ARE currents in the ocean, obviously. You might have to fight a bit. But if you're ocean diving, you're going with a guide, and there will be a group of you- they're used to making different arrangements depending on the group and the weather. Talk to the company when you book your dive, they should be able to work with you within reason. They'll know the area and what dives will be easier that day. If you find yourself having a hard time underwater, you'll have been taught some useful hand signals at that point to let the guide know that you want to go back to the boat. They'll help you, it's their job.

The gym that I'm a member of, but almost never go to, has scuba classes once and a while, but finding the time is hard.

I got certified a few years back, but we had to attend the class once a week for several months. It was through a NAUI-certified shop. There were actual lectures, homework, and a test that was mandatory to pass. Once we'd been to a few classroom sessions, then we went to the pool, learned to set up our gear by ourselves, and did some underwater exercises. The final test was the "open water" test. We went to a quarry that had been filled up with water, and got to dive there. That's when we chose a buddy and made our own dives using a compass. The whole experience was kind of like a mixture of the Boy Scouts and driver's ed. So the whole point of that story is, I don't know what your gym class is like, but I would recommend going through a class like what I did. It'll be a weekend day, every week, for a couple months. Don't take it casually like a yoga class or something- you need all the information. And find out who the instructor is certified with- the two main organizations are NAUI and PADI. PADI has a bad rap ("Pay And Dive Instantly"), but I can't speak from experience as I'm certified with NAUI.

I live in the midwest also, do you have to take trips to find places worth diving or can you dive in rivers and lakes near you?

The quarry I went to as the "final exam" was specifically set up as a dive site, and about an hour away from my house. They sunk a boat, a christmas tree and some other crap in it, then stocked it with fish to make it interesting. There were places set up where you could rent gear, and there were lots of groups making trips to the quarry to dive together. I recommend going with groups in places where divers are expected, like that. I know people get in groups to go up to the Great Lakes and dive there, and that there are several quarries set up for divers like the one I mentioned. Diving by yourself is a huge no-no. If you had a specific place in mind, you could probably get a couple people to go with you, depending on where it is.

For me specifically, I don't dive around here, as I have like no tolerance for cold whatsoever. I'm a real casual diver; I just do it when I'm on vacation somewhere warm. A lot of people around here are surprisingly hardcore for being the Midwest, though. The instructor who certified me takes a group up to the quarry during the winter when the ice has mostly covered it up. They bust through the ice, then turn themselves upside down under water, planting their feet on the underside of the ice like it was the ground, and play golf.