I saw in the trailer some rivers so I'm going to hopefully rightfully assume there will be boats.
And maybe this is already planned but my suggestion involves sort of pirates. On the ocean there would be npc pirate ships you can destroy and loot or what not. And there'd be islands only accessible via boat that might have strong dungeons. Maybe even port towns. Possibly sea monsters like krakens that take multiple people to take down. I don't know if this is planned so that's why I am suggesting it here. Because I know this section is labeled as suggestions for future content for DEO so maybe this would be the Ocean Exploration update later on after release.