I’m probably just dizzy, or dreaming. He turned and saw that the things around him were exactly as they were five minutes ago – his clothes, his fishing equipment, his boat, the lake, the park, the horizon. Yes, the horizon looks normal.
But just two minutes ago, he saw his boat tipping over the horizon, as if it were an insect crawling from one face of a cube to another. Although his entire belief system confirmed with certainty that the Earth is a sphere, he knew that it really happened. His boat really tipped.
The boat rocked a little, and he looked around to see if there was another boat on the lake. A running motor might have caused the disturbance on the water. What he saw instead was a boat exactly like his. There was a man aboard it. He froze when he realized that the man looked exactly like himself.