A balloon is an inflatable flexible bag filled with a gas!  Modern balloons can be made from materials such as rubber, latex, Polychloroprene, or a nylon fabric.  Even a perfect rubber balloon eventually looses their gases to the outside.  Water balloons are thin, small rubber balloons filled with liquid, usually water, instead of gas, and intend to be easily broken.  Large balloons fiiled with hot air or buoyant gas (often hydrogen or helium) have been used as flying machines since the 18th century.  Balloon artists are entertainers who twist and tie inflated tubular balloons into sculptures.