I am lucky enough to have a proper lunch break and at least three times a week I go to a nearby hotel and swim a mile, sometimes 2km.
Today I was alone in the pool and started swimming in lane two (of four) which is one lane away from the side closest to the changing rooms entrance. About 30 min later a man got in and stated to swim in lane 1. Five minutes after that he changed into my lane. I caught up with him at the far end and when he turned he looked at me swimming toward him and seemed surprised (surprised I hadn't moved lanes?). He then kicked off the wall and swam beneath me and under the lane divider into lane three. Not long after I finished up and went to get changed. Before exiting I looked back and sure enough he had moved back into lane two, which I presume is "his". And based on that I believe that he was trying to claim lane 2 when he initially moved in.
He is another regular I have seen him coming as I am going although we don't usually use the pool at the same time.
I think this is knobish behaviour