Besides the land regions (Balenos, Serendia, Calpheon, Mediah, Valencia) of Black Desert Online there is a large waterworld to explore. This includes the islands of the world as well as the oceans them self.
Travel between the islands and continent is possible by private boats or ships or public ones on a schedule. If nodes are connected, then trade ships can move items for the player as well against a fee. Pirates roam the oceans and can cause havoc the same as thieves on land when one is moving trade goods. Soon naval battles will be available.
And there is a rich under-water landscape that can be explored.