Floating bodies
Bodies may float if they do not have ruptured stomachs
Once ruptured, or after decomposition which may take up to 3-4 weeks, they will sink... which is why the big rush was on to find them, and fewer (only one yesterday) are being found.
Autopsy reports also state it is probable that the aircraft hit the water in a near horizontal position because of the majority of 4 fracture type injuries, (ie virtually no head injuries)
Google FAB, the Brazilian Air Force site they have daily press releases and photos in English