Fishermen rowing in the water.

He didn't realize this until he rowed the boat five miles away from the straw hat, which was 1 hour before he lost his straw hat. (5/(5-3+3)= 1)

At this time, he started chasing straw hats, which took 1 hour. (5/(5+3-3)= 1)

If the fisherman loses his straw hat at 2 pm, he finds it at 4 pm.