Pelham,
You are possibly picturing a flat disk floating in space with water spilling off the edge.
That is NOT the correct picture. That is the image use by mockers. It is a straw man argument. Ignore it.
Try this:
A flat disk (like a phonograph record) sitting on a larger flat table. The edge of the disk has an ice wall several hundred feet high.
The water does not “go” anywhere. It is contained.
So... if the ice wall were to get breached, where does the water go?