system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: I've heard pirates drank rum because the water would go rancid. How does water go bad?
gpt
Water unless it has been distilled and is stored in a sterile container that is sealed air tight it is contaminated with various kinds of microorganisms such as bacteria and fungi. These will grow in a stagnant water supply (such as in the water barrels of a ship) and it will eventually get to toxic levels.