I'm in the same boat. PF knocked me out of running this summer so I started riding again and then hopped in the pool. 50m pool and I could just barely make it from one side of the other without drowning. My first outing I did it 8-9 times I think. Went back again a few days later and managed 600m total, still not more than 50m at a time. Kept going back and finally did 100m, then 200m without stopping. Did 1k total!

Yesterday was probably my 20th time swimming and I did 700m without stopping and 2k total. It's gotten way, way easier. I'm pretty slow, but I can breathe and not feel like I'm about to drown.

I watched a lot of youtube videos on proper technique and am just taking my time building up. Like everything else, you just get used to it. My first couple of runs were only 1k, then one day I did 5k, then one day a 10k, etc. After a year and a half I was running 120k/75 mpw. I expect the same for swimming. Just a gradual progression.

Hoping to do my first tri next spring, maybe a sprint or two and then an Olympic. Just bought a P3 with a duraace srm on ebay so that should sort out my cycling (if I can make my legs pedal it fast enough!) .