

Hot take: I think oceans in fantasy worlds have MUCH more potential than most people think.
In a lot of fantasy stories most of the ancient and dangerous stuff is found in places like volcanoes, underground, space, etc... while oceans are just that one place that is used to travel and get food, and I think that's a huge waste of potential.
In OUR world, the oceans contain extremely ancient stuff, creatures bigger than any land animal, and deep sea ecosystems that look like alien planets in comparison to what we have on land. In my opinion, fantasy worlds oceans should be the wildest, most dangerous and cryptid places in the setting.
Just imagine the possibilities: Trenches so deep that they reach hell itself, leviathans so colossal that they make even the most legendary dragons look small in comparison, extremely ancient evils that were sealed in the depths eons ago by civilizations that went extinct before the ocean was even there, gods unknown to the world who are sleeping in the seas and are waiting for some fool to awake them, etc...