How many pools is there in the world?

How much water does an 18 ft round pool with 36 in deep walls hold? Who invented the water polo ball? How good are Jaguars at swimming? How many calories do you burn swimming 1.4km? How do you set up a zone defense in water polo? Where did Michael Phelps train? How do replace the drain cover without draining the pool? Can you swim with contacts? How did swimming strokes get their names? What is leisure swim? How much does dive shop owners make? Are there any swimsuits that have sun protection properties so I don't have to use sunscreen underneath them? How should pool water be treated after finding a dead bird in water? Are there any bodies of water in Wyoming? What are the best spots for surfing in Guatemala? What is the longer form of the possessive sailor's? What floats do people use in swimming? What are the best Above ground pools filters? What is the smallest size in ground pool to accommodate a diving board? How do you troubleshoot a Pool heater?