From Talk Origins
[The Noah's Flood proponents claim:]The order of fossils deposited by Noah's Flood, especially those of marine organisms, can be explained by hydrologic sorting. Fossils of the same size will be sorted together. Heavier and more streamlined forms will be found at lower levels.
Answers In Genesis didn't have much to say on the matter.
(the pic takes you to the search for "hydrologic sorting" which is also blank.)*
Actually to be fair, it comes up in this feed-backquestion[s] and the response contains this:
As far as the “sorting” of fossils, yes, we have a lot of work left to fully explain the existing distribution of fossils. But just because we do not have a complete, immediate answer for this one does not mean the Flood did not do it. The problem is there is a huge amount of information to digest on this topic, and besides, no one really knows what the true fossil distribution is. Many fossil distributions that are vertical on paper are really horizontal on earth and are simply pigeon-holed into slots according to preconceived uniformitarian assumptions. Mr. C references hydrodynamic sorting, but there were many mechanisms that created the fossil record, and hydrodynamic sorting is just one of them (and probably a minor one). Why doesn’t he mention all the gaps in the fossil record, the problem of living fossils, anomalous fossils, out-of-order fossils, the extreme complexity of the trilobite eye, the Cambrian explosion, and other such arguments against uniformitarian interpretations of the fossil record?
So I don't know where they stand on hydrologic sorting
Hydrological sorting is the process by which objects settle in a fluid, often water based on factors such as size and density.
Most seem claims for seem ... vague .. to me. But then, so is my previous sentence.
EDIT: Great search. AIG don't really seem to reference much directly with hydrological sorting or hydrodynamic mixing unless I misunderstood what they were saying. They could be using another term for it too one might suppose.