I've been thinking up an idea of adding a "water" stat that would work similar to "health" (which I'm thinking of re-naming "food").
Water would go down one every one-minute and a player that reaches zero water dies. Drinking from any water source (bucket, well, fountain, pier, canteen, jug) will restore water to full (one hundred).
The "food" stat would be used for combat, so if a player takes a hit it reduces his food level but not the water level (thus, players don't need to carry as much water).
Maybe even have it so that the higher a player's water level, the faster they heal??