Chris's Metal Detecting Page -
Review of the Tesoro Tiger Shark in Salt Water

Chris's Mineral Collecting Page is mainly about [what else?] mineral collecting, but I thought I'd put a little bit of Treasure Hunting stuff up here as well.

In addition to my White's, I also have a Tesoro Tiger Shark.  Now that I've gotten back into detecting, I've noticed a lot of people out there are wondering how the Tiger Shark does in the ocean.  Though I haven't nearly as much experience with detectors as I do with rocks and minerals, I figured I'd do this little writeup anyway, in case it might help someone.
If you are hunting the most heavily-mineralized black sands, the factory-preset Tiger Shark will have an overwhelming number of false signals in the saltwater, especially when the ocean churns up the sand and carries it over the coil.  The way around this is (1) turn down the sensitivity adjustment, which is inside the case (don't open the case anywhere near the water!) and (2) move the coil as slowly as possible. 
The Tiger Shark actually performs very well when there's not that much black sand, even with the sensitivity on medium.  I drove around until I found a beach where the sand appeared relatively free of the stuff.  The Tesoro still had a little bit of chatter and "falsing" in the salt water, but it was pretty obvious when it got a good signal.  A corroded bottlecap about 6-8 inches deep gave a very loud, definite, repeatable signal.  This couldn't be confused with a false reading.   There was no mistaking it.  The same thing happened with a piece of an aluminum beer can and a couple of nails.
So I didn't find any coins in the water;   the wave action had probably worked them much farther down into the sand than I was able to reach.  Based on my finding a bottlecap, small washers, aluminum can fragments, and some nails, I'd have found coins if they had been in that layer (as I said, they're too heavy).  I was detecting in the medium-density junk layer.  The point here is that the Tiger Shark could pick out small targets and get consistent signals, even if there was some chatter.  
I think I might also have run into a couple earring backs or tiny pieces of foil, because something (which gave good, consistent signals) kept escaping my scoop.  It's all too easy to find pieces of metal so small that they fall right through the mesh.

The most important thing to look for when this detector gives any kind of signal in salt water is to see if it's repeatable.  False signals tend to occur under the following conditions in the ocean:

- at the endpoints of each sweep
- when you accidentally hit bottom with the coil
- when you move the coil too abruptly
- when there is too much black sand and bits of rusty iron all over the place

There's a simple way to deal with the first three conditions:  Just focus on the middle portion of each sweep when you hear the signal.  If you get a signal that happens only at the endpoints of your sweep, not in the center, it is a false. 

The fourth condition might mean you'll have to try a different beach, but turning down the sensitivity can help a great deal.  You should still be able to find coins, but you won't be picking up every tiny piece of crumpled-up foil or flake of rusty iron.  Who wants to detect specks of aluminum foil at 10 inches anyway?  The salt water tends to amplify signals, as I've found out over and over again.

Once you master the learning curve for dealing with false signals, processing the audio and visual data through the best computer in the world (your brain), you can get good results with this metal detector in the ocean.  If you try different areas and settings, you can develop a good feel for these techniques in as little as two or three trips out.


Left:  Piece of a very early, hand-forged nail or spike that I found knee-deep in the ocean with my Tesoro Tiger Shark, where the waves had gouged away some of the fine sand and exposed coarser sands and larger seashell fragments.  There were a lot of iron signals there.  This nail was among the strongest;  judging from the clear, consistent sound,  I at first thought it was a coin. 

Some of the water objects were so deep that I gave up digging & just filled them back in.  I still wonder what they might have been.

(Note the pennies and quarters for scale in the photo above.  I found these up in the dry sand after the water got too choppy for my liking.  I'd say the physical action of the waves on me was actually the limiting factor in my water hunting success.  As the wind picked up and the waves got rougher, too many facefuls of water took their toll.  I can't count how many times I dropped the scoop or how many times a wave knocked my coil flat up against the shaft while I was trying to detect.  Even when I was standing sideways to minimize this, it still happened. That ocean can be rough.)

Understandably, some people don't get that excited about things like this nail I found.  They are in the hobby for the gold jewelry.  Gold is nice when one can find it, but an 18th Century forged nail is still a neat find.  Though archaeologically it has little significance, since it's just being tossed about randomly on the waves and gives us no clue of its origin, this old nail is still a piece of an era long gone.  It's remarkable to find something man-made that's at least a couple of hundred years old, lurking amid bottlecaps and pulltabs from just a decade ago.  What story could this nail tell?  What wooden sailing ship might it have helped hold together, a ship now on the bottom of the sea somewhere out there?  What blacksmith hammered this nail out on his anvil?   I wonder what mine the iron came from?  Perhaps one of the magnetite mines of northwestern New Jersey, or maybe even faraway England?  I'll probably never know, though I've thought of taking finds like these to a psychic to see what she has to say about them... no coaching, of course :-)

When a piece of early iron comes up from the water, it often doesn't look as corroded as the newer iron.  For some reason, hand-forged pieces seem more readily to develop a protective coating of black oxide that slows the corrosion process.  Close inspection of the early nail reveals a laminar or striated effect;  this is also characteristic of hand forged iron.








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