Q: Is it possible to tell if victims died from drowning and the time of death of remains found in water?
A: yes, for sure there are several ways to tell if the victims were drowned. One of the ways, that is also help determine the time of death of remains found in water is to evaluate the diatom level.
Diatom refers to a diverse group of algae. It has no specific structure or characteristics as it is consider a general term of groups of algae that inhabit the remains. Yet, the migration of diatoms, meaning the sequences of diatoms in the body should tell the time of the body in the water by calculating the schedule.
The same applies to the drowning victim too! Yet, during the drowning process, victim should also have inhaled some of the fresh water (only in fresh water will find diatoms!). So in the lungs, ME should be able to find fresh water and diatoms for calculation, as well as backward calculating the appearance of diatoms in order to work out the time of death.
P.s. Diatoms belongs to the Forensic limnology department, which is a sub-discipline of forensic botany, fyi : ) !