Yes, water is playable
...and is worth 8 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Water" Definition
noun
A body of water such as a sea, lake, river, or stream.
A clear, colorless, odorless, and tasteless liquid, H2O, essential for most plant and animal life and the most widely used of all solvents. Freezing point 0°C (32°F); boiling point 100°C (212°F); specific gravity (4°C) 1.0000; weight per gallon (15°C) 8.338 pounds (3.782 kilograms).
A fluid present in a body part in abnormal quantities as a result of injury or disease: water on the knee.
A particular stretch of sea or ocean, especially that of a state or country: escorted out of British waters.
verb
To moisten, sprinkle, or soak with water.
To supply with water for drink.
To treat with or as if with water.
To impart a lustrous appearance and wavy pattern to (cloth) by calendering.
idiom
Above water Out of difficulty or trouble.
Water under the bridge A past occurrence, especially something unfortunate, that cannot be undone or rectified: All that is now just water under the bridge.
verb-transitive
To dilute or weaken by adding water: a bar serving whiskey that had been watered.
To give a sheen to the surface of (silk, linen, or metal).
To give drinking water to.
To increase (the number of shares of stock) without increasing the value of the assets represented.
verb-intransitive
To drink water, as an animal.
To produce or discharge fluid, as from the eyes.
To salivate in anticipation of food: The wonderful aroma from the kitchen makes my mouth water.
To take on a supply of water, as a ship.