Waterproof metal detectors are designed specifically for metal detecting in the water, although many all-terrain metal detectors serve a multifunctional purpose. Treasure Coast Metal Detectors carries all the major brands of waterproof metal detectors, some as much as 200 feet deep. In contrast, other metal detector waterproof tools are only suitable for a depth of 15 feet. The thrill of metal detecting in the water will provide incredible metal-detecting finds. Here in Florida, a big rush is finding something from the Spanish 1715 fleet.