If you have access to a pool, swimming is wonderful. There are a lot of great cardio workouts you can do from your living room. I use an on-demand service that has a ton of options. If you have a gym membership or access to a Y, use the exercise bikes or rowing machines.
I like aqua aerobics. It’s easy on the joints. I can do lunges and lots of squats. I can even jog in the water. And I do not have to lay down at all. But I’m sore the next day so I know it’s working.