FWIW I had a coworker once who lost a fair bit of weight swimming. He had also been injured, and gained a lot of weight, so swimming worked for him at losing weight without reinjuring himself.

Re: motivation in general, I'd suggest getting a Fitbit or similar watch, along with their automated scale. Weigh yourself regularly and let their system keep track of what you are gaining and losing. Similarly, keep track of how many steps you are taking and how active you are.

Personally I've found that the most effective way for me to lose weight has been to incorporate it into a commute with cycling... I was a lot skinnier when I had a 9-5 office job and biked to work. Unfortunately, that's not easy to replicate for many people, including myself!

Secondly, in general I've found that exercise is much more effective for me than diet. I already eat reasonably healthy, and don't lose weight; specialty diets like carnivore are just too limiting to stick too. But every time I consistently exercise for awhile, I quickly lose weight as long as I keep that up. Doesn't even take much: just running reasonably hard for 15 minutes a few times a week is enough.

Good luck!