My contribution:

The other day, I head to the pool to do some laps. Posted rules are that two swimmers share a lane; three or more circle swim. There are also posted lane speeds - slow, medium, fast - which are often ignored.

As it happens, every lane has two swimmers of greatly different speeds, meaning that circle swimming will be annoying. (I'll circle swim, but I prefer it to be with people of similar speed). I'm not in a huge rush, so I opt just to wait. And a few minutes later, someone departs a lane, leaving a single pool-runner.

[He's pool-running while clasping a basketball (not a water polo ball) to his chest, but that's not the basis for this story, just an odd aside.]

I walk over to that lane, dip my legs in, and ask the pool-runner if we can split and which side he prefers.

"Circle swim only! You always circle swim. It's rude to other people not too."

I explain to him that the posted rules are that two people split, but he's not having it. I also explain that if we try to do circles, since he's pool-running and I'm swimming, it will be hard for me not to run into him. He responds that that's my problem, and that I need to learn to share and to swim around other people. His voice gets elevated.

I get up, walk over to one of the lifeguards, and ask her whether we should split or circle swim. She confirms that splitting is correct and it would be odd to circle swim with just the two of us. I then return and explain to him that the lifeguard prefers that we split, but he's still not having it.

"Circle swim only!" Loudly.

About that time, another swimmer exits a different lane. Great, I'll just swim there. Issue solved, I think.

Except that this action enrages him even more, and he loudly berates me for my selfishness and unwillingness to share the pool with others as I walk across the deck. In his view, I am a horrible person.

It was just really odd, and a bit disturbing.