Congrats on getting started The start is the hardest. Just get into a routine now and don't let other put you off
Regarding weight loss/bad knee, not to take the threa off topic, but have you considered cycling?
Cheers. Planning to go Mon/Wed/Fri morning before work.
I have cycled in the past, but the problem I found with it was it just takes up too much time. A good run out would involve a good few hours and with work and two youngs kids I couldn't commit that much time.
I used to get up before work and run a few miles 3 times a week, but I had my ACL rebuilt a few years ago and this last year it's been giving me more bother so I've stopped with the road running, but the early mornings, while the rest of the house was still sleeping worked well, hence why swimming came into my head.
Ticks the boxes in terms of low impact on knee, not too time consuming and can get it down before work.