When I learned that I had been selected to field test the new Tesoro Tiger Shark, I was excited, to say the least. The Tiger Shark is the newest addition to the Tesoro line of water detectors, replacing the popular Stingray series of machines. Its arrival has been anxiously awaited.

I have been using Tesoro machines since 1984, and over the years, I have used many different models. It did not take long at all for me to be impressed by their silent search operation and their great discrimination. Over time, I came to respect the great quality of their machines and their great service department.

When I bought my first Tesoro water machine in January 1997, I had been using another well-known brand for over six years. I decided to go with a Tesoro water machine because I was tired of digging hundreds of nails every week, and I really liked the idea of having interchangeable searchcoils. The fact that they also had a reputation for being good at finding small gold rings and chains was simply an added "plus." In 6 years with my previous water machine, I never found a single gold chain. In my first year with the Tesoro, I found 3-and one was 24K!

Unfortunately, living in Wisconsin would preclude me from being able to test its saltwater capabilities.


The Tiger Shark is a true dual mode water machine using microprocessor technology. It has a Salt Mode to be used only for wet salt sand or salt water hunting and a Normal Mode for fresh water or dry land hunting. The two different modes use completely different internal settings and cannot be interchanged. On dry land, it can be used for coin, relic, or even gold prospecting.

The Tiger Shark pole assembly breaks down into three pieces for ease of storage and travelling. It is the popular S-style pole design with a padded handle grip and arm bracket, and it has an adjustable Velcro arm loop. All three pieces fit together with interlocking spring buttons and the top two sections each have a locking-bushing that eliminates any chance of pole wobble. To convert the pole assembly to a diver version, you simply remove the center pole section.

The Tiger Shark can be assembled in several different configurations. The control housing can be mounted to the pole assembly in two different locations or worn on a belt utilizing the built-in slots. It can be clipped to the pole assembly directly under the arm or directly in front of the hand grip area where the controls can be easily adjusted while hunting. The pole assembly has spring buttons in both locations for easy attachment and removal of the control housing.

The Tiger Shark comes standard with an 8" round open center concentric coil with an 8' cable length. Tesoro also offers a 7" and a 10½" version, and scuff covers are available for each. One great feature of the Tesoro underwater coils is that they are all fully interchangeable. This terrific feature is exclusive to the Tesoro line of water machines and no other detector manufacturer has yet to match it. Users of the older Stingray line of machines can also use their existing coils on the Tiger Shark.

Its operating frequency is 12.5kHz, and the audio frequency is approximately 270 Hz. Total weight is less than 4½ pounds, and the optimum operating temperature range is from 30°F to 100°F. It is a silent search motion discrimination machine with a maximum depth rating of 200 ft.

The control housing comes with Bilsom waterproof headphones that are permanently attached to the unit. The housing is the familiar molded case found on previous Tesoro water machines, and it has proven itself to be extremely rugged. The faceplate attaches to the unit with two drawbolts and has a ribbon cable assembly connecting the inner electronics to the faceplate controls. There is ample length to the cable assembly to allow the unit to be completely opened making it very easy to change the batteries. Water leaks in the cover or the coil connection have been virtually unheard of.

An 8 cell, AA size "drop-in" battery pack is contained within the unit. To reach it, you simply unlatch the faceplate, open the unit and it easily slides right out with a tilting of the housing. Tesoro recommends alkaline batteries as opposed to rechargeable type batteries and I have to agree. When rechargeable batteries begin to go, they go very fast offering little reaction time for the user. It is never "nice" to be surprised by dead batteries, especially with a water machine, because you can't just carry spares around and replace them while standing in the water. It usually means you have to trek back to your vehicle and dry everything off. Alkaline batteries die much slower, allowing the operator a greater chance to react. When sealing the unit back up, you should always inspect the O-ring seal, ensuring it is kept clean and free of dirt or sand, and periodically lubricate it with the silicone grease supplied with your new unit.

Another feature of the Tiger Shark is its audio response on shallow vs. deep targets. The engineers at Tesoro made a minor modification to the circuitry, which created a distinct loud tone on all targets up to 5 or 6 inches in depth, and a more muffled tone for targets beyond that depth. I have always paid great attention to the very faint signals of deep targets, but it was easy to mistake the faint "blip" of a good target with the faint "tick" of a discriminated piece of junk, especially in very trashy areas. With this distinct audio difference, it is much easier to recognize a deeper "good" target from a piece of trash. As with all Tesoros, the most important characteristic of any audio response is if it is constant and repeatable. If you get a constant and repeatable audio response in both the left-to-right and top-to-bottom sweep, dig it. It makes no difference if it is faint or loud. If it is repeatable, you should dig it.

The Tiger Shark, like all Tesoro machines, has a limited lifetime warranty. It is one of the main reasons I originally bought a Tesoro, and why I continue to buy Tesoros today. To me it is an immediate indication of good quality and service and that a company stands behind its product.

The last nice feature of the Tiger Shark is the operator manual. Too many manuals offer you only the method of "how" to tune your machine and don't elaborate on the "why this is important" aspect. To become proficient with any new machine, you need to know what it is telling you and why, thereby offering you the best opportunity to react. The better you know how your machine works, the better the two of you will perform together. The Tesoro manuals offer insightful explanations to both the "how" and the "why," and they use lots of photographs to clarify and explain.


There are four different control knobs on the face of the Tiger Shark: TUNE SPEED (All Metal Slow, All Metal Fast, Motion Discrimination), MODE (Of/Off, Normal, Salt), DISCRIMINATION LEVEL (1 through 10), and GROUND ADJUST. The two all metal modes (Slow and Fast) are non-motion modes. There are also three controls internally that can be adjusted, and I will talk about them later. The unit also performs a battery test each time it is turned on, emitting a series of audible "beeps." When the batteries are fully charged, you will hear 6 or 7 beeps. As the battery power weakens so does the number of beeps at power-up. When you only hear 1 or 2 beeps, it's time to change your batteries.

Simply put, you can hunt in either NORMAL or SALT mode, and within each of those two modes, you can hunt in either ALL METAL or DISCRIMINATION.

The TUNING SPEED knob has two settings in all metal, SLOW and FAST, plus the MOTION DISC position. The SLOW and FAST all metal positions refer to the speed at which your threshold tone re-tunes itself. ALL METAL FAST should retune in about 1 to 2 seconds after a target response, and ALL METAL SLOW may take 4 to 6 seconds to retune. You only hear a threshold sound when you are in all metal mode.

Operating the Tiger Shark is very simple. The most important adjustment you must always make is setting the GROUND ADJUST properly. Ground balancing is a simple but very important skill that you must master in order to operate the machine at its peak performance. Tuning your machine to the exact ground matrix that you are hunting in will give you the best possible depth and stability. I won't go into the fine details of ground balancing, other than to say that it is a very simple task and that the procedure is well explained in the operator manual. Once the unit has been ground balanced, you may then switch to MOTION DISC, set your DISC LEVEL, and begin hunting.

The operator manual also walks you through a simple air test procedure, so that you can actually see where different targets are knocked out by the different discrimination level settings. I think this method is much better than simply listing a chart of numerical settings in the manual because there can be minor differences in these settings from one machine to another, and because most of us are not all that good at memorizing numbers. It is much more important to know how to test your own machine to determine those settings than it is to remember the numbers listed somewhere in a chart in your manual, which is probably at home when you really need it.

The three internal controls that can be adjusted are the VOLUME, THRESHOLD, and SENSITIVITY. These controls are preset at the factory for optimum performance but can be adjusted if necessary. It is Tesoro's belief that once set, these controls almost never need adjusting, so they put them inside the unit where they would not be accidentally bumped or altered. Ample instructions are given in the manual, including pictures, should you need to adjust any of these controls. You will need a very fine jeweler's screw driver (Phillips) to make these adjustments.


The biggest challenge that I faced in testing the Tiger Shark was in trying to find a water site that contained even a small amount of targets. I received the Tiger Shark in the last week of April, and I had a two week time frame in which to test it. Here in Wisconsin, the swimming season is directly related to the water temperature, and at this time of year, no one has been swimming since the beaches closed last September. Our swimming season starts around the end of May or early June and continues on into early September. There are some brave souls that push beyond those limits but not many because the water gets pretty cold up here. Our lakes usually freeze over by December, and then open back up around March. This varies quite a bit depending on the winter. My hometown of Madison is blessed with four lakes and 18 staffed beaches (manned with lifeguards), as well as at least a dozen other sites that are "unofficial" swimming areas. It is also home to the Four Lakes Metal Detector Club, which has at least 14 members that are active water hunters, including myself. Let's just say that the beaches in Madison get pounded, and they get pounded very hard! At this time of year, our beaches are amazingly void of targets, good or bad! It was still too cold for a wetsuit so waders were the order of the day, which meant I would not be able to hunt the deeper areas of the beaches.

I decided my first site should be one that I was familiar with, an area that I knew was not loaded with a lot of trash. I picked a site on the north side of Madison-Warner Park. This area is one of the "unofficial" beaches that I mentioned earlier, very popular back in the 40's when Madison was home to a large contingent of the United States Air Force stationed at nearby Truax Airfield. The Airmen frequented this spot often during their off-hours and over the years, I have done quite well here, along with other members of our Madison club. This site is well known by the water hunters, and it has been hit very hard. It has a very long shoreline with a nice sandy bottom. I spent about 3 hours here and although I did not make any major find, I was impressed with the number of items I did find. I hunted with the DISC set at 5 and found a number of copper rivets, copper nails and washers, as well as some sinkers, a .32 cal. shell casing, a kid's ring, a brass button, 10 memorial cents, a 1944 cent, 2 dimes and 1 quarter. Not too bad for April in Wisconsin.

My next spot would be my own private site, one that I am sure no one else has hunted. Last fall I discovered a previously unknown beach area that had been used in the late 40's and early 50's. It was a small neighborhood beach, and it did not see a lot of activity, but none the less, it contained some nice items. It had long since been a swimming area and now was merely a lakeside park. I worked it extensively last fall, every weekend, and had pretty much cleaned it out. I ended up getting 5 gold rings from this area before the targets became depleted and the lakes iced over. I had previously only used an 8" coil on this site, so it would be a good comparison to go over it again using the Tiger Shark with its 8" coil. The area is rocky near the shoreline but then nice and sandy as you get out to hip-deep water and beyond. There was a pier at this site as well, and the biggest concentration of past finds came from that area. I ended up spending about 3 hours here, eventually wandering over to a nearby residential pier. Again I set the DISC at 5 and again I was impressed that I was finding any targets at all since I personally had this spot "cleaned out." I found a brass key, sinkers, a bullet, 9 memorial cents, 3 wheaties (36D, 40, 46), 1 nickel, 2 dimes, and nice cast lead Indian riding a horse, and a cast lead elk. Fair amounts of trash were recovered at this site, usually coming up in the same scoop with a good target. I also had 3 nice marbles come up in my scoop.

The following day I felt a lot more comfortable with the machine, so I decided to try a new spot. I drove to Rock Lake, 30 miles east of Madison, and hunted a street-end park (where the road ends at the lake). These are common swimming areas and quite often contain a good amount of coins and sometimes jewelry. I had seen signs indicating that this was a one-time swimming area and decided to give it a closer look. Again, I set the DISC at 5. I was disappointed to learn that the bottom here was nothing but rocks! Undaunted, I hunted anyway. It would not be the first time I dug in nothing but rocks, nor would it be the last. I found a rather large concentration of targets with very little trash. I recovered a brass key, a kid's religious ring and a religious pendant (gold plated), a sterling friendship ring, a very small silver chain, 31 cents, 3 nickels, 1 dime, and 3 quarters. I spent about 2 hours here before the rocky bottom wore me out.

My final day of testing was made back in Madison, starting at the hardest hit beach in town-Vilas. This is the most popular beach, historically containing the most jewelry, but also getting hit the hardest by all the local water hunters. It would be a true test of the Tiger Shark's ability. The last time I hunted this was late last fall, and I dug only 3 coins. I opted to use the 10.5" coil for this hunt, and this time I turned the DISC down a notch to 4. I recall wavering, not sure if I should even waste my time here, but I pushed on and headed out into the water. On my very first pass toward deep water, I dug a kid's adjustable ring. I wondered out loud how it had been missed up to this point. As I continued into deeper water, I got a faint but nice signal at the limit of my waders in chest deep water. It was faint but a very nice repeatable signal. I was delighted and surprised to find a cute little gold ring in the corner of my scoop. It had spots for two stones, but only one pretty pink amethyst now remained. Bingo! I was now grinning from ear to ear. I turned and headed back towards shore and within 5 minutes had another faint but repeatable signal. This target turned out to be a 1945-S war nickel! Sweet! It must have been on edge for it was not that deep. I now continued towards shore and in about 12" of water, I again got a nice signal. To my total delight and amazement, yet another gold ring comes up in my scoop! Now I am giddy and laughing out loud! I certainly did not expect these kinds of finds, not here, not at this time of the year! This one was a 10K ring with a badly worn green stone (Marquee cut), definitely of an older design style. What a great start! I couldn't believe my good fortune! My next target read as two signals next to each other, one strong, one weaker. In this scoop, I found a bottle cap and small silver cross on a once-plated chain! I remember that suddenly one word popped into my mind-predator. This aptly named Tiger Shark was a real predator!

I continued hunting for another hour or so, and although I made no more gold finds, I did find a fair amount of targets from this heavily hunted beach. I added a silver earring, 2 kids' rings, a .22 cal. shell casing, 2 buckles, 4 memorial cents, and 1 quarter. That doesn't sound like much, but again, this beach had been pounded very hard! It is also worth noting that this beach is on a very small lake (Wingra) and the bottom here has never been subject to shifting or moving like you might see in larger lakes with strong currents. The targets I found were not "uncovered" by moving sands over the winter months.

I then journeyed to one last site-another hard hit popular beach in Madison, B.B. Clarke beach. I spent a little more than an hour there and found one key, a sinker, 3 memorials, a 1951 wheatie, 1 dime, and 4 quarters. This is more in line with what I had hoped to find but still impressive considering the time of year, and I did wonder how 4 quarters were missed by previous hunters.


I have to believe that the ground balancing feature of the Tiger Shark is one of its more important features. In the sites I hunted, it certainly seemed to give me a greater target depth and a greater amount of sensitivity. Even the deepest targets were easily noted to have nice repeatable signals. Nearly all of the "border line" signals I dug turned out to be trash items. I was impressed on several occasions to dig up a single bobby pin. Some people may say they don't want a machine that hears every bobby pin, but not me. In hard-hit beaches, I want my machine to be capable of finding bobby pins, because then I know I won't be missing any gold chains! To me it's an indication that the machine is tuned properly and doing a good job! With this machine, you do not need to slow your normal sweep speed just to hear the deep targets. You may need to slow your sweep down to pinpoint them, but I did notice that the target response was always sharp and immediate.

I also believe that a good number of the coins I found during this test had to have been on edge or at some slant. Nearly all came up in a single scoop, and as I previously noted all but one site had been pounded relentlessly for months. I can come to no other conclusion as to how so many quarters were missed by previous hunters, among them myself, and none seemed to have been blanked by nearby trash because they were the only targets in my scoop when each was found. I also had several multiple finds, when two pennies came up in the same scoop. Targets of that nature are not easily missed by the hoard of hunters that have pounded these sites. At a number of locations, I was able to pick good targets out of heavy trash areas, without too much difficulty. It requires a slower sweep pattern to more readily separate the good from bad but easily achieved, and this is one of the areas where this machine really shines. As far as its ability to find small gold rings, I proved that as well. The first gold ring I found was only a size 2½, barely fitting the tip of my pinky finger.

It takes very little to convince me about the great iron masking circuitry that Tesoro is known for, and it is immediately obvious when you have previously hunted with one of the "other" brands of water machines. I am speaking of the water hunter's bane, nails! Ask the veteran water hunters, the ones that have used the older machines and the ones that have used the "other" machines, and they will tell you harrowing stories of digging thousands of nails. I am not sure that the Tiger Shark can detect a small gold ring any better than the competition can, but I am sure that it will pick it out of beach littered with nails while the competition only hears it as one "beep" amid many. If you can't isolate it, you can't dig it. In my book that means more gold rings for me. I always chuckle now when I see a nail in my scoop because I know there is a good target in there someplace as well. Yes, you will hear the larger nails and the galvanized roofing nails, but the majority you will pass right over without ever knowing they exist.

The 3-piece pole assembly makes it a dream to pack for your seaside vacation, and having interchangeable search coils is a feature still unmatched by any other major manufacturer of water hunting machines. I prefer the 10½" coil for the added depth, especially at very clean beaches, while the 8" coil works better when hunting trashier sites. I prefer to belt-mount the control housing, but the other mounting combinations make this machine very versatile.

As far as versatility is concerned, you probably noticed an earlier comment about also using this machine on land for coins, relics, and gold prospecting. That was a quote I took right out of the operator manual, so the people at Tesoro certainly believe it has merit. Even though the Tiger Shark is advertised as a water machine, I was very interested in testing it further on dry land for relics and coins. I may not get the opportunity to test its nugget hunting skills, but I certainly would give it a try if the situation arose. I see no reason why this machine would not be great for coins and relics, especially with the ground balancing feature. It sure seems to add greater depth in the water sites I tested. Not surprisingly, an air test comparison I did between the Tiger Shark and the Toltec II resulted in nearly identical readings between the two.

On my last weekend available for testing, I decided to try it out on land at a ghost town site I have been hunting. Bad weather and a minor illness only allowed me about four hours of hunting time so I don't feel qualified to give it a fair rating. I was able to find an 1895 Indian cent (badly corroded) and a 1944 Mercury dime, but not much else. I was pleased enough with its operation that I definitely want to test it further. Could this be the first machine that is truly good on both land and in water? I will have to get back to you on that one (but all indications are good!)

Thank you, Tesoro, for affording me the wonderful opportunity to test the newest addition to your family!

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