Captain of a ship telling this interesting story

The captain of a ship was telling this interesting story:
"We traveled the sea far and wide. At one time, two of my sailors were standing on opposite sides of the ship.
One was looking west and the other one east. And at the same time, they could see each other clearly."
How can that be possible?

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The marines were standing back against the sides of the ship so they were looking at each other.
It does not matter where the ship is