I was doing a running HIIT routine for a little while but I had knee surgery a while back so it started to get pretty painful and I had to stop. What I've been doing the last couple weeks is essentially HIIT in the pool. I will all out sprint for 20 seconds (I swam competitively in high school so it's a pretty good sprint.) then rest for 1 minute and repeat this for 25 minutes. Warm up/cool down not included in the 25 min. What do you guys think of this as a replacement for running? I'm mainly interested in the fat loss, more so than the cardiovascular benefits.