Types of Metal Detecting Activities, page 23:
UNDERWATER METAL DETECTING
General Information, Tips, Metal Detectors and Equipment
Underwater Metal Detecting refers to the following three activities:
1) Snorkeling with a Metal Detector - treasure hunting while using a snorkel and a diving mask in salt or freshwater which is usually less than 6ft deep. Snorkeling may be also associated with surf wading or wading in a lake or river. This type of underwater detecting does not require much of equipment and physical strength.
2) Scuba Detecting - metal detecting in fresh and saltwater which is usually less than 20ft deep while using a scuba gear. One needs some training and additional equipment to do scuba detecting.
3) Shipwreck Diving includes both treasure hunting in the area around a shipwreck and searching for valuable artifacts inside the sunken ships. Shipwreck diving can be done either in shallow water or in deep water down to 200 feet.
Shipwreck diving is the most costly type of treasure hunting as it requires a lot of expensive equipment and gear, not to mention just a dive boat especially modified for it. As shipwreck diving presents many challenges to a treasure diver physically and mentally, a considerable amount of experience and knowledge in operating scuba gear is required. It is also the most dangerous type of treasure hunting; however, with highest risks come highest pay-offs: one dive can make you a millionaire.
1) SNORKELING WITH A METAL DETECTOR
First, you need to learn and master snorkeling! Snorkeling with a metal detector requires that there should be at least a couple feet of good visibility underwater. Depending on climate or geographical zone, surfs will differ considerably. For example, the continental surf is different than the surf in Hawaii, and the Atlantic surf in New England is not the same as in Florida considering just the water temperature difference. Also, snorkeling in the ocean or sea surf is easier since the salt water's density is higher than of fresh water.
Snorkeling with a metal detector is usually done at the water depth ranging from chest-deep, where people play/throw balls, play "Marco Polo" and other similar games, and wrestle/horse around, to just above your head, where the swimmers have to swim the first few strokes.
When snorkeling in the ocean or sea surf, go with the flow of the water currents and let them push you back and forth. You should pay attention to the valleys, low spots and around rocks on the bottom. The gold valuables tend to occupy these places more than others. Plus, unlike the less moving water in lakes and ponds, the ocean water currents create a constantly moving environment which helps gold jewelry find the lowest spots faster, and redeposit valuables continuously.
As for rocks and other obstacles on the bottom, water will pile up sand on one side of an obstacle and wash it away from the other side. This is why the gold rings are often deposited next to the rock. Obviously, rings are more plentiful in the area closer to shore. So is the trash which is positioned in the shallow layers of the sand, and gold valuables tend to go deeper. Therefore, one should dig deep to get to them.
Avoid snorkeling with a metal detector in the tropical and subtropical ocean surf at night as you may encounter a sting ray. Sting rays will not bother you, but getting electrocuted by them is not a good idea. Night hunting in lakes and ponds may be not a great idea also because of snakes that can be very harmful.
Underwater Metal Detecting and Target Recovery Techniques
During the process, try to follow an imaginary line or a real line set up on the bottom with a rope and sand screws. Then move back and forth about 5-6 feet to either side. Pay close attention to the bottom "pot holes" and dig every target they may contain.
When in sand that is less than five inches deep, swing the search coil in a semi-circular motion in front of you at a moderate speed, and overlap slightly. When in deep sand, slow down the speed of the sweeps and listen for "tiny" and deep signals.
If you use a multi-tone ID metal detector, utilize zero discrimination and dig all but iron targets. Sensitivity should be at maximum but not too high if you want your metal detector remain stable producing no false signals.
Zero discrimination and maximum sensitivity settings will provide the greatest operational depth range which is necessary to detect gold targets. Although recovering them requires digging down deep, it is much easier and quicker to dig deep in the water than on land. This presents an advantage of underwater metal detecting.
Some snorkeling treasure hunters use long wood-handled steel trowels for recovering targets from the rocky or hard clay bottom. The stainless steel is strong enough to withstand hard hits against rocks and does not rust.
The long wood handle lessens the weight, is more comfortable to use, and saves your knuckles from getting skinned by corals or rocks (coral cuts do not heal very well and burn painfully). The trowel handles most digging jobs quite well.
If you recover targets mostly in the sand, you can simply fan the silt sand and small rocks away with your hand or a small paddle like a ping-pong bat. The larger the search coil of your metal detector, the more area you need to fan.
While fanning the sand, you should constantly scan the recovery spot to see if the target has moved. If you fan or dig in the same direction, the current will usually carry any sediment away, leaving decent visibility in the hole.
Or you can use the long trowel to fan the water in the hole when you almost reach the target while digging it up from deep sand. The hydraulic action will preserve the find. It will take a little more time to get to the target, but the rewards are great.
A screw driver is used to pry coins out of cracks and holes. A modified sand screw may be used for recovering targets from a thick layer, up to several feet, of sand. This tool can solve the problem of sand filling up the hole faster than you can excavate it.
Where To Hunt
It is important to choose the most visited locations to increase the odds of finding valuables. For this type of underwater metal detection, areas where there are heavy concentrations of people in or over the water would the most productive.
Such areas are swimming holes, deep surf along popular beach areas, piers and docks. Special attention should be given to spots around piers and platforms/boards from which people jump into the water; the higher the structure, the better your search results! Give an area where not many people swim or dive the last priority.
