Sorry to intervene, but I find this to be a very interesting topic, and I think I can add something to it. I must say I never asked myself your question, Robosteve, so I had to wrap my head around this in order to be able to explain what's going on.
You say that the RET is faulty, because it says that gravity varies from place to place, which would lead to the ocean water flooding certain places and leave others dry. Well, in fact, the mean sea levels have quite a respectable difference in different places on the earth because of local differences in gravity. Thus, the sea level at places with higher gravity due to more mass within the earth, such as the indian ocean, actually is 85 meters higher than the worldwide average. In places with a less dense core, such as northeast of Australia (thinner magma => less mass => less gravity), the sea level is 100 meters lower than the worldwide average sea level.
Now, why doesn't the water flow from the indian ocean to above Australia then? Well, why does water level out anyway? It does because of gravity. Gravity states that a water plane has to be level, because it pulls the water towards the earth's surface equally. But if you have local differences in gravity, you will have local differences in the water plane as well. Therefore, the mean sea level is not entirely constant over the earth.