On your side of the coast, it's always said the closer to the "center" you get, the less likely you'll ever make it back. Mana Storms, sea monsters, ghost ships, and pirates tend to make that area particularly risky. There's word that the center of the ocean has an isle untouched by any civilization for years, but most take these as simply tales for the foolish, since most seasoned sailors assure that the only thing around there are sunken boats. Which itself could be quite a bounty if you know how to get to them.