[legacynl]

True. The body is perfectly capable of telling you when it needs water, it's called being thirsty. If you're thirsty, drink, otherwise don't.

[lurking_swe]

sort of correct. As one ages the body starts doing a poor job of signaling thirst.

https://medlineplus.gov/ency/article/003086.htm

> As people age, they are less likely to notice their thirst. Therefore, they may not drink fluids when needed.