What is a poison? … Carrots, water, and oxygen are “not poison”. … (… You’re really asking about fatality from metabolic disruption, after administering doses small enough to avoid mechanical damage and blockage, at room temperature, at low velocity.)
If I understand that last definition correctly, it should classify water as a poison.
Nitpicking your poison category:
If I understand that last definition correctly, it should classify water as a poison.