Alright, assuming the Earth is flat and is accelerating upwards towards the ocean, due to the property of inertia, the ocean itself would match the acceleration of the earth and would not have anything to hold it down.
For that matter, why is the force that is supposedly making the Earth accelerate upwards NOT affecting the oceans in the flat earth model? Wouldn't it be reasonable to assume that the force that causes the Earth to accelerate upwards also causes the ocean to accelerate upwards with it? And in that case, in your proposition, the oceans would NOT be held down by the acceleration of the earth, and should have floated away by now.
Water is matter, just like everything else. Matter has mass. Gravity exerts force on all mass, pulling it down to the Earth. The oceans are held down by the same force that holds down our atmosphere. Even if water molecules are perfectly buoyant, gravity would hold down the entire system as a whole, even if it has no effect on individual molecules within the system.
I notice that you... tend to selectively argue the points of Round-Earthers. I've given a proposition as to why the earth accelerating upwards could not hold down the ocean, and I've given a counter-proposal as to how a Round-Earth model (unmodified, mind you) can hold down the oceans. If you bother to argue with me, seeing as how you try to avoid arguing against good points, remember not to quote anything out of context, kay thanks.