Hi Jim,
Google herschbach tdi
I believe the shipwrecks info is on the White's Surf Dual as there is not yet an underwater TDI.
Hoser John - long time no chat! Glad to hear the TDI is working for you. It is a real bang for the buck unit.
The single biggest advantage of the TDI over the Infinium is coil selection. Since it is Minelab coil compatible you have almost 100 coils available for the TDI. But you want waterproof, get the Infinium.
I've got a GPX-4500 and it is a fine unit but frankly not everyone has $5000 to spend on a metal detector. If somebody had told me 10 years ago I'd have a $5000 detector I would have laughed at them! You can get both a White's GMT and a TDI for less than half what you'll spend to get the GPX-4500 and have yourself one great nugget hunting combo.
I run a pay-to-mine operation at Moore Creek and needed some units to provide to our customers who do not own a detector. We have some fairly magnetic hot rocks at the mine and so PI is the way to go. The Minelabs, with the harnesses and bungees and power cords are just not the sort of detector I want to hand out to people who will be dragging them through the mud and the brush. Not to mention the sheer cost of four units. The TDI also had the advantage of coming with two batteries, so we can always have one battery charging while the detector is being used.
The bottom line is the TDI is a solid, capable detector. It is not a GPX-4500 but it was never intended to be. The TDI is about value, and for $1500 you get two drop-in batteries, a waterproof coil, built-in speaker, and ability to hip or chest mount right out of the box.
Anyway, if you are seriously into nugget hunting and have the money and want the best, spring for the Minelab. But if all I used was the TDI I'd do just fine. It is certainly easier to recoup the cost - the first nugget I found with mine paid for it!
Steve Herschbach
Here is a nice 2.07 oz. specimen found at Moore Creek last summer with the White's TDI by Chris P from Soldotna, Alaska.