we know _nothing_ about the oceans. Even the things one would think are pretty easy are known at very, very coarse granularity. "what shape is the ocean floor? what's it made of? how deep is the sediment here?" are questions that, for the vast majority of the ocean, we have answers for at a resolution of about one data point per square mile or worse, and that survey data is decades old.
The last "proper", "get on a boat for 6 months and count animals" surveys of marine mammal populations in some high risk areas of the ocean (like the gulf of mexico) are almost 40 years old for some species.
etc.