Most dinosaurs were man-sized or smaller critters, and if their nearest relatives, crocodiles and birds, are any indication, about as dense as modern animals. A two-meter long velociraptor therefore probably weighed in the neighborhood of 45 kg (remember, one meter is tail). A 1.8 meter human male weighs on the order of 80 kg. Note, they are both approximately the same density. Therefore, the Flood should have sorted the remains of velociraptors above those of humans -- but we don't see this in the actual fossil record.
You're ignoring the possibility that humans are probably better swimmers than velociraptors.
You're saying that the velociraptor is Bigger than a man, weighs less and therefore should be above the man by weight.
Your assumption is based on what - as weight goes. If you're right about the weight, then your conclusion is well founded. If you are not, lets just say, at .2 meters bigger than the average man and given the weight of gators, I don't find it credible that a Raptor would weigh less than a man. Nor would I base my conclusions on single instances with regard to the fossil record. By and large, the sorting of fossils is far more indicative of bouyancy sorting. The sorting of the strata can also be accounted for in this manner along with the difference in the strata world wide.