Bring the water and salt to a light simmer over medium to high heat.
Unroll the crescent roll dough. Cut into thin strips.
Cook on very low heat, stirring frequently for 20-30 minutes. If you need to add liquid, you can add a little more water. The texture should be smooth and creamy but thick once it is cooked.
Add the butter; let it melt and gently stir it into the polenta.