Regular pools usually disinfect the water inside of them using chlorine–but not Disney. They use bromine, which is a fancy, more expensive, and much milder smelling chemical (and is not as harsh as chlorine when it hits your skin or clothing).

The water at Walt Disney World and Disneyland is treated with a combination of chemicals to ensure safety and clarity, but it is most famous for its distinct "Disney smell," primarily caused by bromine. Unlike the chlorine used in most public pools, bromine is more stable at higher temperatures and is less irritating to the skin and eyes, making it ideal for the massive volumes of water in attractions like Pirates of the Caribbean and it’s a small world. In addition to bromine, Disney uses standard municipal water treatment chemicals such as sodium hypochlorite (liquid bleach) for general disinfection, poly aluminium chloride as a coagulant to remove cloudiness, and activated carbon to eliminate odors and tastes. For the more natural water bodies, such as the Seven Seas Lagoon, Disney employs specialized algaecides and dye to maintain a deep blue appearance and prevent the growth of invasive aquatic plants.