[zolthrowaway]

It really depends on context. If you have a bunch of people sharing one lane at a rec center, yes, you could be a huge jerk if you constantly were forcing people to stop by touching their feet. If there is one other person in your lane and there isn't a massive skill gap, touching their feet and having them stop is perfectly reasonable.

I swam in college. I was a distance swimmer. We would have warmups during the break with people from all sorts of different teams at different skill levels doing different events. When I'm warming up for the 1650 and there are sprinters in my lane, they are going to touch my feet a lot. That is just part of it. It takes literally a second for them to pass and allows them to do what they need to do. Context is key for sure, but in general feet touching is the international sign of please let me pass in swimming.

[cattlefarmer]

How does this work?

Aren't you usually furiously kicking/flapping with your legs when swimming?

Are they actually touching the bottom of your feet, ie your soles? Do they have to time it right to not get kicked?

[zolthrowaway]

For freestyle (front crawl), it's more of a scissor kick. Your whole body turns with you so it's really easy to touch the sole of the foot heading toward the bottom of the pool. When someone is doing something like breaststroke, they're doing a frog kick which is generally going out and away from the body and then pulling the legs in, you just time it so you touch their feet when they pull their legs in.