I quite literally was thinking as I was reading your second paragraph, "hey, they should try swimming" - turns out you're well ahead of me!
I started about four years ago, and it's been awesome for me too. For me I tried it because I just never liked how running makes me feel in my chest, whereas the aerobic intensity of swimming (slower burn in zones 2 and 3) feels way better to me.
For anyone starting out, there is a bit of a hump to get over as you get some technique (I just used YouTube videos and feel). For a bit of an idea of how it can be to start, when my then-girlfriend (now wife) started coming along to some of my sessions, she had done three half marathons and was training for her fourth, but she couldn't swim 50m of freestyle in one go without a break! I remember doing two laps, having a break, then some breastroke, break, etc., whereas now I can pretty easily punch out 600m freestyle sets fairly fast before a break, or do 2km without stopping at a bit of a slower pace.
I started about four years ago, and it's been awesome for me too. For me I tried it because I just never liked how running makes me feel in my chest, whereas the aerobic intensity of swimming (slower burn in zones 2 and 3) feels way better to me.
For anyone starting out, there is a bit of a hump to get over as you get some technique (I just used YouTube videos and feel). For a bit of an idea of how it can be to start, when my then-girlfriend (now wife) started coming along to some of my sessions, she had done three half marathons and was training for her fourth, but she couldn't swim 50m of freestyle in one go without a break! I remember doing two laps, having a break, then some breastroke, break, etc., whereas now I can pretty easily punch out 600m freestyle sets fairly fast before a break, or do 2km without stopping at a bit of a slower pace.