There are a variety of underwater metal detectors available on the market today.
When choosing a model you'll need to decide whether you will be underwater metal detecting fully submerged while scuba diving, or whether you will use the detector at the waters edge.
Obviously, if you intend to fully submerge the metal detector you'll need to ensure that all of its components are fully waterproof. Remember also to check the depth to which they are rated. Most fully underwater metal detectors are rated to 100 or 200 ft. These will suit all but the most experienced of scuba divers and professional treasure hunters.
If you are intending to use the machine at the waters edge where only the coil will be underwater, detectors classed as 'waterproof' will be sufficient.
Once you've decided upon the use of the detector you'll then to need to decide on the type.
Types of Underwater Metal Detectors
In general, these are the four main types of underwater metal detectors are currently sold online and in stores.
1. Pulse Induction (PI)
Pulse induction metal detectors function by emitting a series of electronic pulses into the ground beneath them. The pulse circuit goes deeply into the ground through the water.
The pulses, which are short and quick, are quite sensitive to precious metals. However, they are not affected by ground minerals or wet sand. This makes them ideal for saltwater environments such as beaches.
The drawback is that this type of detector does not discriminate well between trash and treasure. This may lead to just as many poor finds as valuable discoveries. Pulse induction metal detectors perform well no matter what type of ground condition exists.
PI metal detectors do tend to be more expensive than their VLF brothers. However, heir increased effectiveness in marine environments is often regarded as outweighing their extra cost.
2. Very Low Frequency (VLF)
Very low frequency metal detectors function using a low frequency range of 3 to 30 kHz. This style of detector has good discriminating capability and can determine coins relics and jewelry from trash. Unfortunately, this style of detector can be affected by minerals contained in the ground or sand.
To overcome this, many of these models offer a sensitivity adjustment as well as a ground-balance adjustment. This provides an opportunity to tweak your settings based on your findings. If you do decide on a VLF style detector, be sure that it offers a salt water mode.
3. Beat Frequency Oscillation (BFO)
This is a very basic system and are generally used for very cheap or budget metal detectors. Essentially they are two rings of copper around iron or steel with a current passing between the two. The current is sent into the ground and if the signal is broken an audible beep is sent to the user.
The main thing to remember is that they have no way of discriminating between trash and a good find. They might be useful for those on a very tight budget or as a starter but for the serious metal detecting enthusiast I'd generally recommend they be avoided.
4. Broad Band Spectrum (BBS)
Broad band spectrum metal detectors function using a broad band of signals, emitted in more than one frequency. Capable of emitting up to 17 different frequencies, broad band spectrum metal detectors offer good discriminating capabilities. Since they use a range of frequencies they can identify a target more accurately. They can detect at varying depths better than a single frequency detector.
Additionally, false signals from salt water beaches and ground minerals are reduced. BBS metal detector technology has now been phased out, but I've included it in the case of anyone buying an older second hand metal detector.
What Can You Find With Underwater Metal Detectors?
Wherever people gather they lose things! People gather on beaches they lie on the sand and things fall out of their pocket and get buried by sand quickly.
The most common item of 'treasure' to be found will be coins. In beach environment these are most likely to be present day coins, old silver or gold coins will be an exceptional find on a beach.
Folks also swim in the ocean and a mixture of sunscreen and the cool water causing finger shrinkage means that rings can often slip off and be lost. Until found by you!
Of course, if the ring has any identifying marks that may identify their owner such as a name then all efforts should be made to return the ring to its rightful owner. However, in practice this is going to be rarely possible.
Underwater Metal Detecting Accessories
In addition to your detector there are a few basic accessories you should have.
These are essential to filter out background noise and hear the subtle signals that may otherwise be drowned out by ambient noise. Most detectors will come with a standard set of headphones, but of course you might want to upgrade from the basic set.
You'll need something to dig the sand around your target in order to locate your find.
A sand scoop will greatly assist you locate your discovery and speed up the process. A sand scoop is a simple sieve, fine enough to allow sand to pass but coarse enough to securely hold on to your find.
A simple pouch or utility belt is a useful accessory to hold your finds. You'd probably rather not fill your pockets with sandy finds.
There's nothing worse than your batteries running out of charge halfway through your session. Remember to carry some fully charged spares.
A pinpointer is an optional extra. Some people prefer them others prefer the sand scoop method. You'll certainly need a pin pointer when treasure hunting in soil so you may already own one. But for beach and ocean hunting a sand scoop is quicker and just as effective.
Metal Detector Bag or Cover
Since you'll have several items it makes sense to also purchase a metal detector bag or cover. This will keep all your things together and keep them protected.