AstraMike:
I thought it was well established that it took a while, days in fact, depending on surrounding temperature, before a human body would float. Equally, the conditions below the surface are different than those on the surface.
Therefore you cannot base constant drift assumptions on the bodies, until they surface
Hi,
This is what most people think but, having being involved in several sea rescue operations in the past, I can tell you that it isn't true (or partially wrong) from direct experience. Sorry for the following details.
Like any objects in water, there is three cases: sink, float or stall.
It is based on the differential between object and sea water specific gravity. In clear water, the tendency for the large majority of humans (+90%) is to sink, because their specific gravity is higher than clear water (0.97) but in standard sea water (1.027), it is the contrary and the majority of human (+70%) is naturaly buoyant. Some will have an equal gravity and stall close to the surface but 100% submerged for some time. The buoyancy of most human is very close to 0, say 0.01 meaning that only 1% of the body will surface and it will be almost invisible at some distance.
Now, when one sink, he will go to the bottom and, if deep enough, he will never re-surface because of high pressure compressing the human body added to higher density of deep and cold water. In tropical seas, the high temperature of water means lower density and a higher sink rate.
Plenty of factors will affect people buoyancy (like age, gender, physical condition, etc.) but the most important one, considering disasters at sea, will be the clothing which may affect buoyancy one way or the other. Victims will usually float face down, with a very small part of their back immerged during several days, then they will start to turn belly up after some time, depending of the sea temperature.
In conclusion, it is nearly impossible to predict how many people will surface
immediately following a disaster and it is very common to miss some of them until they reach some very remote coastal areas, sometime after drifting for months over several thousand of milles.
S~
Olivier