Swimming will definitely help to keep your cardiovascular up, but do keep in mind that you will probably lose some strength from riding just because you haven't been riding, so you haven't been able to train those muscles. But since you're in good shape, it shouldn't be more than a few weeks to get your fitness levels back to what it used to be on your bike as long as you stay consistent with your riding once you get back into the riding.

Cross training is great- as long as you continue to do both sports. You'll be able to recover from one activity while you train the other, which will be tremendous benefit to your body. Just make sure you're maintaining your level of intensity with your cycling and with your swimming. What I mean is, if you're working at 70- 85% heart rate max for your cycling one week, then go to swimming the next week, when you get back to cycling, make sure you're still doing the 70- 85% max heart rate for your cycling. You cannot let up on what you decide to be your training intensity at all.

You're definitely going to be a more well-rounded athlete from all this training you're doing! Good job.

Koffee