An oceanic question

[Anomalocaris]

The Challenger Deep is the deepest known area of the ocean.

But I was just thinking, is it at all possible for there to be parts of the ocean where there is no bottom seabed? Is it possible for the ocean to span downward all the way to the opposite side of the globe?

It's a great question, how much water lies below the crust of the Earth:

https://en.m.wikipedia.org/wiki/Deep_Carbon_Observatory

and, with it, life.  What amazes me is that there are bacteria, via Darwinian natural selection, that have slowed their metabolism down to thousands of years for cell division to survive deep underground.

some estimates put the amount of water chemically sequestered in the mantle of the earth to be equal to several times the amount of liquid water in the world’s oceans plus the surface fresh water and ground water in the crust.

much of the volcanos around the pacific ring of fire and in the mediterranean are believed to be caused by water brought down into the mantle of the earth by plate tectonics chemically combining with mantle rock and lowering their melting point, which allows them to melt and mobilize upward as magma to erupt as lava through volcanos.

people talk about water cycle through the air.  but the water cycle through the mantle of the earth facilitated plate tectonics and thus sculpted the earth far more profoundly.