The whole ocean can't freeze-only by dropping the air temperature.
The problem is that the Earth is hot inside.
It freezes minus two degrees Celsius - the surface.
That ice becomes a blanket-protects the deep water.
Down in the dark-the pressure is heavy, freezing point drops lower.
The (core) is the biggest problem for ice-Vents push out heat, a constant thing.
To freeze the abyss you have to kill the planet first.
Have to shut off the inside furnace - We have to wait billions of years for the rock to go cold.
The ocean.
It stays liquid.
It will continue because the Earth is still alive - the physics will not let it happen yet. It is impossible now.