How to escape the endless ocean in "Way of the Nether"?

There is a single island in the Overworld; the ocean stretches out on all sides of it. You can't really watch which direction the clouds are moving, because they move too slow to make out while swimming, and you'll drown if you try to watch them from the bottom of the ocean long enough. Even if you could tell which direction they were moving, this wouldn't tell you which way the island was. If you didn't happen to have a compass or map (which it's likely you don't), you'll either have to swim around in a spiral hoping to hit land and hope that everyone else will finish the quest and/or be able to switch into creative mode. Otherwise, try drowning and see if you respawn in the village.