Swimming in a pool can be a lot like being in your own bubble. This is one of the reasons why I started to really like swimming as an exercise when I begun with triathlon. I had to concentrate so hard on just the act of swimming that I forgot about the world when doing it. For me this is the ultimate thought killer, and a great way to clear my head if I'm worried or stressed. But it's also my biggest downfall when it comes to improving myself, because of the limits of feedback you'll get from your own consciousness.
I watch a lot of swimming videos on youtube about how to swim correctly, and I feel like I'm progressing every time I enter the water. The problem is though that even though my times are improving, and I don't know if that is because of my technique getting better or if it has to do with me just straining myself a bit more.
Last time I was at the local swimming pool I was lucky enough to meet a guy from the local triathlon club, and although he doesn't swim that beautifully himself he gave me a lot of good tips on how to improve. I knew all the things he said I was doing was wrong, but I didn't know I was doing them. He cleared up my head and made me realize that swimming with people probably is the best way for a swimmer to improve.
The reason for this is the constant feedback you'll get while being in the pool. Filming yourself is one thing, but when you get feedback in the pool you'll be able to correct you technique and start improving at once.
This realization has made me certain that I'll need to join sessions together with other people soon, cause I want to dominate the swimming from Alcatraz.