You might be surprised to learn that water guns have been around for a long time - they were even mentioned during the Civil War. Yes, seriously! The oldest reference to a squirt gun is from 1896 and it comes from General William T. Sherman: "Why, you might as well attempt to put out the flames of a burning house with a squirt gun."
Back then, squirt guns were made from cast iron and they resembled actual handguns. Manufacturers soon picked up on the trend of liquid-style pistols and started manufacturing them out of plastic for the kid's market.
Today, water guns are a summertime staple that comes in all shapes and sizes with various release mechanisms and designs. You can get anything from a water blaster, a pistol, a squirt gun, and even a grenade-style water blaster. The primary function, other than to shoot water and thoroughly drench your opponent in water, is just to have lots of good old-fashioned outdoor fun.