Yeah, seen that too. Once I had two coming right at me. They were prone and swimming fast! I tried shooting them and with no effect I suddenly thought I need a harpoon. Then they got "stuck" and suddenly vanished.
I've also seen the same happening in areas where you just know that they haven't been shot. Like from spawn points. First I thought it only happens when someone gets shot and they die after the lag, but people spawning and then doing the magical swim doesn't really support it. Lag me thinks.
