1.18.2 / (Addon) Water Flasks / Flask Materials
Central to effective water storage is reuse of something that stored water(ish) before.
Bladders!
Only certain animals have bladders that work for this purpose, and some species' are easier to extract than others.
Animal___________Chance
Sheep___________________10%
Alpaca__________________10%
Goat____________________10%
Equines_________________20%
Bears___________________20%
Bovines_________________50%
To increase your chances, use a higher damage weapon to butcher the animal.
Flask Sides are used in both flask recipes.