A human corpse that has been buried for five years is likely to still have skin and other tissues visible on its skeleton, according to Memorial Pages. However internal organs and eyes, all of which are composed largely of water, tend to liquefy and decompose quickly and are therefore unlikely to be present.
According to Memorial Pages, it takes eight to 12 years for the average unembalmed adult corpse to decompose to a skeletal state. However, the type of material used to construct the coffin affects this time considerably, with oak extending the decomposition process by up to 50 years. If a corpse is embalmed, its decomposition can be slowed significantly, as embalming chemicals repel pests and bacteria. Other factors that affect decomposition time include the depth of burial, the type of soil and the water table.
Memorial Pages points out still other decomposition variables such as humidity; average heat or cold; the type of clothing a body is buried in; accessibility to insects, rodents and other pests; and the availability of oxygen within the grave. Because of these variables, there is no definitive formula to predict precisely how a corpse might look after a given number of years buried.