There some myths about drowning.
For instance, people do not scream when they are drowning because of the physiology of human body when water has entered the mouth and causes the epiglottis to close over the airway. The victim will continue struggle but they can't make any noise as he/she cannot breath.
I will skip the five stages of drowning at here and focus more on the investigation parts. If the pathologist has been asked to perform an autopsy on a body that was found in water but does not have any physical injuries or problems with heart disease, then it mostly likely conclusion as misadventure.
The basic concept of investigating a drowning case would be checking on the lungs whether it filled with water, but there may well be occasions when it proves difficult to establish whether or not the deceased was alive when they entered the water; this is because when the individual is submerged long enough in the water, the lungs will fill up anyway. The other aspect of looking into death occur before or after drowning could be checking on the diatoms in the body systems known as forensic limnology.
Forensic limnology is another sub-field of forensic botany, which examines the presence of diatoms in crime scene samples and victims. Different methods are used to collect this data but all identify the ratios of different diatom colonies present in samples and match those sample with locations at the crime scene.
Layman : Different water area exits different species of diatoms. Diatoms is a kind of "living thing" known as a single-celled species of algae with " shells " made of silica. Therefore, if a person die while he/she still alive, courtesy to the cardiovascular system, the heart pumps blood to all over the body, when the water comes into the body, diatoms may be available in lungs, liver, as well as kidney. Thus it is a more accurate way to determine if someone has drown before or after death. And that is forensic limnology. Diatoms are well preserved in decompose body !
For the decomposed corpses and skeletonise body found in water, the diagnosis of drowning is rather difficult because those "drowning signs" were destroyed. Here the diatom test stand as the only direct screening test for drowning. Malaysia pioneer study about diatom was started by Hospital Kuantan.
Occasionally a condition called " dry drowning " may present itself; this is where the deceased's larynx has gone into spasm as water has entered the throat, thus the passage to the lungs is blocked and any water that is already in there cannot get out and more water cannot get in.
Another phenomena known as " secondary drowning ". Layman : drown again after the first time exposure. A tiny amount of water enters the lungs causing irritation and the fluid produced in the lungs as a result can accumulate to cause drowning up to 72 hours after the exposure. Therefore, do not be careless after saving someone from the water. Be more specific, it is due to the electrolyte disturbance metabolic acidosis occur.
Antemortem = subject to water before death
Postmortem = subject to water after death
