I was thinking (dangerous, I know), that the weight lifting days are going to be 45 - 60 minutes, but the cardio days are 20 minutes. Would it be OK to do a few laps in the pool after the cardio workout?

I'm a real water baby, and I love to swim. I haven’t swum in a while though, between no pool access and looking like the great white fuzzy whale.

Or, could swimming be done as part of the cardio? Not sure if that would work, but I know I used to be winded and had a good "rush" after 20-30 minutes in the pool doing laps.

I don't see why you couldn't use it for cardio.. just memorize the sequence of intensities you are supposed to hit and get a waterproof watch so you can keep an eye on the time. I was thinking of trying the pool for cardio because I have a preview pass to a local gym with a pool but I haven't got around to it yet. Let us know how it works out for you if you try it!

Swimming always kicks my butt!!! I think it would be an awesome form of cardio. Just make sure that you can get in a lane that nobody gets in your way so you don't mess up your workout.

Wee

It's fine to add moderate cardio any day.

Oh, the good news, fat floats! I love to swim too!

Piano

I agree with nitrowixen, swiming can be your cardio. And yes, you do need a waterproof watch. (Better: a waterproof heart rate monitor?) If you have the proper technique/speed you can do the same hiit. According my experience, there is one difference. When I swim I need a longer "warm up" time, than with any other cardio, before starting the hiit.
And I agree with Wee, try to find a pool where there are different lanes for different level swimming, so slower swimmers do not hold your back.