While they have records; maybe her teeth were lost in the lake due to her being so decomposed?
A body in water will usually sink but because the specific gravity of a body is
very close to that of water then small variations e.g. air trapped in clothing have a
considerable effect on buoyancy. Having sunk to the bottom the body will remain
there until putrefactive gas formation decreases the specific gravity of the body
and creates sufficient buoyancy to allow it to rise to the surface and float. Heavy
clothing and weights attached to the body may delay but will not usually prevent
the body rising. Putrefaction proceeds at a slower rate in water than in air, in sea
water than in fresh water and in running water than in stagnant water. The
principal determinant is the temperature of the water so that in deep very cold
water e.g. the North American Great Lakes or the ocean the body may never
resurface.
In the water the body floats face down with the head lower than the rest of the
body so that lividity is most prominent on the head, neck and anterior chest.
Lividity is often blotchy and irregularly distributed reflecting movement of the
body in water. It is not intensive and appears a pink or light red colour. In cold
water it can be dusky and cyanotic. It may be difficult to recognise due to
swelling with water of the upper layers of the skin with resultant loss of
translucency.
Once removed from water putrefactive changes advance with remarkable
rapidity. Adipocere which is a soap-like transformation of subcutaneous fat is common in
bodies immersed in water usually appearing after some months; it may be present
in as little as six weeks.
http://www.dundee.ac.uk/forensicmedicine/notes/water.pdf
