I have a hard time "working out" due to a blown out football knee(no cartilage left) from back in the day and the subsequent damage to the other knee from years of overcompensation due to the "bad" knee.
I'm not in that bad of shape knee wise, but I've spent just shy of 50 yrs pounding the snot out of my knees. I've always been very conscious of wanting to NOT make them worse by beating them up worse working out. I do 0 running (one of the more destructive exercises for your body), but I hit the wall where walking up steep hills gets too easy, too fast, as I'm always in somewhat decent walking shape from all the ridges I bust.
I rely on two things for cardio that are fairly low impact on the knees. Jacob's Ladder (picture a conveyer belt bringing hay up to the mow, only with wooden dowels from rungs. You bear crawl up, using hands and feet, but stay in one place) will wipe you out in less than 120 seconds the first time you do it, and I mean wipe you out, and that includes all those 110 lbs little girls that ride the ellipticals for 2345876981274 hrs straight, without breaking a sweat or taking a deep breath. I love/hate the thing, as it gives me the exact benefits I'm going for, but it is pure hell. Even when I'm peaking, 15ish mins straight is about the best I've ever done, and you can literally ring a quart of sweat from my cloths after 5 mins. It sucks getting to that point, but busting the steepest, tallest ridge, Buffalo Co type ridges don't even get you to breath hard when you get to that point, and I never feel any knee strain from it.
Since you may not want to invest in a piece of EQ (no clue how much it costs, as I do that at the gym), the other thing I do a bunch of is bike type work. The wife convinced me to take a Spin Class with her years ago. she hated it, but it was a good fit for my knees. You can emulate the same type of workout simply riding a bike or picking up a comparatively cheap (as exercise EQ goes) adaptor for a bike to allow you to bike in place inside during winter. It's not as but kicking as Jacob's ladder, but it gives me a lot better workout than walking and is very low impact on my knees. I can still make myself breath hard doing that, well after I'm in "busting ridges" shape. That may help compliment the swimming for you or replace it all together, if you decide the drive/$ is too much. At $85, you could buy the adapter for the bike in 2 months and have paid for a hell of a nice bike in 4-6 more months....and you wouldn't have to drive to work out....Just a thought.