I think adding a water bar and a new item called a water bottle that you spawn with would make add another challenge in Minecraft to overcome. The water bar would run out fast, so it makes a desert have a use besides sand. I also think there needs to be a water bar because having water is something that you cannot survive without in real life, and therefore it shouldn't be overlooked that water isn't needed in Minecraft. Some of the last updates have mostly been added more decoration stuff (except 1.9) but nothing that changes survival styles, so i think adding drinkable water will make the updates more fun. The icon for water bars can be either drops or water buckets.

There can be an effect for walking in deserts and running called thirst, and it depletes the water bar faster, like hunger.

I think there should be a difference between freshwater and saltwater. Any pools of water or small lakes or rivers would be freshwater and therefore drinkable, but big oceans any bay would be saltwater and hardly fill your water bar and give side effects, like nausea or slowness or something. Saltwater could even have a different texture, like a dark blue or have a green tint to it.

There would also be craftable water bottles that hold more water so it fills your bar more. water bottles could be crafted out of 7 clay in a cauldron shape. The clay water bottle fills up 2 drops The best water bottle could be made out of 7 iron and fill up half (five drops) of your water bar. Once your water bar depletes you get slowness one, then a few seconds you get slowness 2 and nausea, then you get slowness 3, and then u die of thirst.