You people don't understand!
There are clouds in the game! And the rain from the clouds is necessary to have a sea and realistic looking waves. Otherwise the ships couldn't even swim without all that water.
...at least that's how I read it.
“It appeared that there had even been demonstrations to thank Big Brother for raising the chocolate ration to twenty grams a week. And only yesterday, he reflected, it had been announced that the ration was to be reduced to twenty grams a week. Was it possible that they could swallow that, after only twenty-four hours? Yes, they swallowed it.”
- George Orwell, ‘1984’