How To Metal Detect Underwater

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Cory Haasnoot

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Have you ever wondered how metal detectors work underwater? You are in luck because in this article I will explain how underwater metal detecting works and some of the amazing items you can find under the waves.

Do metal detectors work underwater? The short answer to that question is yes, metal detectors work underwater. But you need a special type of metal detector to detect underwater and I will explore more on how that works.

Two Types of Underwater Metal Detectors

There are two types of metal detectors that you can use to metal detect at the beach and under the water. They are:

Pulse Induction (PI)

The pulse induction metal detectors will send electronic pulses into the ground. These detectors typically have a single, double or triple search coil that works as the transmitter and receiver.

With a PI system, short pulses of current are sent through the search coil. A magnetic field is produced with each pulse sent. An electrical spike happens when the pulse ends. 

After that, a second electrical current called a reflected pulse is sent through the search coil that only lasts around 30 microseconds. Once that is done the process starts over.

When a PI metal detector detects a metal object a pulse is created of an opposite magnetic field. A reflected pulse will be created when the magnetic field collapses. The metal object will cause the reflected pulse to take longer to disappear causing you to hear a distinct sound that notifies you of a hit.

To better understand the process of a pulse induction metal detector. Picture yourself in a big room that has no hard services and you yell. The echo of the yell will not last long because of the lack of hard services. If you are in a room full of hard objects and you yell the echo will last longer because of the objects.

In a PI metal detector, the echo from objects that it detects is added to the reflected pulse making that pulse last longer then it would if an object was there.

Pulse induction detectors electronic currents are not affected by salt water and the minerals in the sand and silt but they are very receptive to precious metals. So PI detectors are best for metal detecting in saltwater. The only problem with pulse induction detectors is that they have a hard time deciphering the junk you will find from the treasure.

Very-Low-Frequency (VLF)

The other type of underwater metal detector is called very-low-frequency or VLF. Like the name suggests these metal detectors use a low frequency to detect metal objects underwater and in the sand. VLF detectors are best used in a freshwater setting.

VLF detectors use two coils an inner coil called a receiver coil and an outer coil that acts as a transmitter. The transmitter coil sends an electrical current through the wire one way first and then sends another one the opposite way. This is done a thousand times a second.

The receiver coil acts as an antenna that captures the frequency signal that the transmitter coil gives off. 

Unlike the pulse induction detectors, the VLF detectors can easily discriminate what is junk and what is a treasure. But on the flip side of that coin, they have a harder time telling the difference between ground minerals and precious metals. 

If you have the right adjustments on your VLF then you can minimize the interference of the ground minerals. So essentially PI and VLF metal detectors are opposites to one another when it comes to there pros and cons.

Scuba Diving

First, before you can even think about metal detecting underwater you will want to have experience with scuba diving or at least be able to snorkel. Once you have acquired these skills then it’s just a matter of picking the right underwater metal detector and practicing diving and metal detecting

Once you have attained both these skills you can make some very valuable finds if you detect in the right places. 

Metal Detecting In The Shallow

Many a ship has come aground over the centuries so even if you are just combing the shallow areas around the ocean or great lakes you can find quite a bit of treasure that’s hidden beneath.

If you aren’t a scuba diver or can’t afford scuba equipment then metal detecting in shallow waters is a great option and sometimes you can find just as much in the shallow areas then you would in the deep.

How To Use An Underwater Metal Detector Effectively

Metal detecting underwater is not as easy as it sounds. You need to be able to handle the metal detector while swimming if you are scuba diving and it can get very tiresome so you won’t want to underwater metal detect for long periods of time.

If you’re in the shallow water it’s best to wait for low tide because this is when you will find the most objects. Working with the tide current will allow you to know where the sands shift and you will find metal objects more easily this way.

Keep in mind that unfortunately, you will more than likely find a lot of junk, metal detecting underwater and to be a good steward of the seas you will want to take that junk out of the water. You will be doing the environment a big favor though.

What Accessories Do I Need For Metal Detecting Underwater?

In order to go metal detecting under the waves, you are going to need a few tools that will make the process much easier in the long run. You will want a good pair of waterproof headphones so that you can cancel out all external noise so that you can hear the signals clearly as they come in.

You will need a trowel for digging along the beach. A  long-handled sand scoop for the deeper waters and a beach sand sifter scoop. You will also want a wet bag that you can tie to your waist or scuba gear. Make sure you get one that ties closed so you don’t lose any treasure before you are done.

If you are snorkeling or diving make sure that the metal detector that you have comes with a short dive pole which makes life much easier and comfortable on your dive.

How Deep Should You Go?

You don’t have to go hundreds of feet deep to find valuable objects. The ideal depth is between one to six feet of water. So if you focus on these depths you won’t need to know how to scuba dive.

There are those that do underwater archaeology with metal detectors 100 feet down or more but you are talking big bucks and you need permission to do a dig like that. But for the novice detectorist, all you need is an underwater metal detector and 1-6 feet of water and your good to go. It also helps to know how to swim.

Your Underwater Adventure Begins

Now that you know how to metal detect underwater you could have yourself an adventure of a lifetime. There so much buried beneath the sands of all the water bodies on our planet it boggles the mind.

Once you have the right equipment to metal detect underwater you could make some amazing finds. To this day I’m amazed at the sunken ships that have been found and all the pirates loot that has been brought up from the open seas.

Just remember that you don’t need to be a scuba diver to go detecting in the water. The perfect depth is between 1 and 6 feet of water. There is plenty you can find in shallow water thanks to the currents of the waves.

Underwater metal detectors can also be used on dry land as well. So you have the best of both worlds. So get out there and start exploring the deep! Who knows what you will find buried beneath the waves.

I hope you enjoyed and learned something from this article. If you have any questions or comments please leave them below. As always Happy Treasure Hunting!

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Author: Cory Haasnoot

Cory Haasnoot is an author, entrepreneur, metal detecting enthusiast, antique, coin collector, and founder of Treasure Seekr.

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