Blowers (also known as “Mailboxes”) are one of the main tools utilized in areas less than 50 feet, deep where there is significant overburden to be removed. Mel Fisher is generally credited with inventing this technique. Originally it was intended to deflect the propeller thrust towards the bottom to carry clear water to the divers working in poor visibility. It worked so well that it began to excavate holes in the bottom sediment. Over the years the design has been improved, and it is one of the primary ways you can recognize a “treasure ship” today. If it has giant tubes with a 90 degree angle mounted on the stern, then it is most likely a treasure hunting/salvage vessel.