A water balloon or water bomb is a latex rubber balloon filled with water. They are commonly used in water balloon fights and as a practical joke device. The first commercially marketed water balloon was produced by Edgar Ellington in 1950, while trying to invent a waterproof sock to solve the disease known as trench foot. The design for the sock was a latex coating over a normal cotton sock. When the invention was up to his standards for testing he tried wearing the sock but then quickly found out the elasticity of the latex made it difficult to put on. After ripping several pairs of his waterproof sock he finally managed to successfully put the sock on by carefully heating the sock with a indirect heat source. He was thrilled with his success and had taken off the sock and filled it with water and tied the top to make sure that he had not accidentally ripped the sock unknowingly. When he did this he saw a small stream of water spurt out of the balloon.
Contributions by Scott Boise, TheKMan, and Achowat.