As a mere mammal, it's hard to comprehend the scale of things like the earth. The crust on the ocean floor is "only" about six to twelve kilometers thick. This is only one one-thousandths to two one-thousandths of the earth's radius. It might as well be a drop of sweat entering a crack on your chapped lips by comparison. Some would get into the lithosphere, but that's still quite near the surface, again, next to everything else.

Once you get past the crust, and then the various layers of the mantle, to the liquidy bits, well ... the density is so high that water would be completely forced to float to the top even if you could get the water down there. Plus it would be exposed to high temperatures and might well be steam (depending on local pressures).