I filled the base with sand and use it in my jacuzzi. I put my 9' tilt crank umbrella in it. It works just great and cheaper than purchasing a "European Sun" umbrella that swivels on it's base. They run about $1,000.00 or more! 
Before we used to get out of the jacuzzi earlier because we didn't want to get too much sun exposure. Now we can stay out there as long as we want.