Due to the pressure in the water being higher than in the center (the momentum of an individual molecule forces it outwards), a higher column of water is supported at the rim.
The speeds involved are not relativistic, so this isn't a matter of special or general relativity. Except, of course, one needs to explain the conservation of momentum relative to the universe. Noether said that's because space is isotropic.
I think there are a few 'fringe' modern-ish physics projects that actually do suggest that space could be made from something, and can flow (which can provide an explanation for gravity and relativity) Reg Cahill's "Process Physics" (from a while back) had a good crack at this I reckon and more recently Wolfram's work around graph-rewriting operations as a model for fundamental-space.. which sounded like it went pretty well!
The speeds involved are not relativistic, so this isn't a matter of special or general relativity. Except, of course, one needs to explain the conservation of momentum relative to the universe. Noether said that's because space is isotropic.