You've obviously been tricked by the magic of the great Mit the Creator
The world is flat, so to prevent us from falling off into oblivion he installed a quantum electrodynamic quadropole-tandem temporal manipulation field around the perimeter of the land to teleport us to the opposite end when we go threw it. The Pac Man games use a similar process, which the programmers learned about from the great Mit.
If you notice, the ocean vanishes after you get out a bit. The reason it doesn't all drain away is also due to this field.