Many planets out there will be water worlds. Those generally come in two flavors: either the oceans are so deep that the water turns into high-pressure ices like ice-six, -seven, -ten and -eleven or they aren't, leading to worlds with rocky seafloors.
On a world with Terran gravity, ice-six would from at a depth of ca. 63 km. The oceans of Ganymede and Titan probably have these kinds of icy seafloors. So since there are ice-free and endlessly icy seafloors, I was wondering about the borderline case. Let's say a planet with global oceans with a depth of 63 +/- 6 kilometers. I'd imagine that this would result in rocky highlands and seamounts and ice-plains in the lowlands and trenches.
However, I was wondering how the boundary between ice-six and water would actually look like. Would it be a sharp distinction, like a smooth ice-plain or rather uneven and like the underwater side of ice-bergs? Or would there be a slushy transition zone with poorly defined borders? Or something totally different?
Additionally, should I think of ice-six just as dense ice or is seeing it as rock made out of water a more accurate description?