In order from least to most dense, it must be: C, B, A and D. Seawater with high temperature causes an object to float, while seawater with low temperature sinks or is denser than high temperature. Salinity is also a factor to determine density; the higher the salinity, the denser the water. In terms of depth, it seems that sample D is the deepest part while sample A is the shallowest. This is determined because temperature drops significantly with depth.