Underwater metal detectors are very popular today, because any virgin territory thats left for metal detecting is probably in swimming spots. Plus there is a lot of jewelry lost by people while swimming, or around swimming areas. This makes metal detecting in these areas very productive sometimes, and of course the metal detector manufacturers have capitalized on this occurrence.
The problem the metal detector makers ran into right away was the problem all designers and engineers run into when water and its properties are added to any functionality equation. Water may not be all pervasive, but it is close. This makes for some very interesting, dare we say annoying, circumstances? Yes we certainly do dare say annoying, and perhaps we may even go so far as to use the word dastardly, if not despicable, when referring to water and its effects on electronic circuitry. Oh yeah, we could go on and on and ON in our negative descriptions; anyone who has had experience with all this has invented a few malicious remarks of their own I am sure...this type of thing could elicit creativity-in-cursing from a dead man; suffice to say waterproofing anything is a Major PITA, and that does not mean a type of bread.
My first underwater detector leaked three times before it finally went to heaven. All three leaks were my fault, because I did not put the unit back together as well as I should have after changing the batteries. Another common cause of leaks is going beyond the detector housings endurance depth, meaning too deep, so that water pressure forces moisture in through the o-ring seal. The first mistake, not putting the detector back together correctly after changing the batteries, is by far the most common of the two. I have heard of housings getting cracked and causing leaks, but thats rare, when compared to the first two reasons.
This article is addressing the two most common leakage problems, as mentioned above. There really is no help for a cracked detector housing/case except to replace the whole unit. I should mention here that sometimes, if a leak is discovered quickly enough, and is caused by a bad seal, versus a cracked housing, then the interior can be rinsed and dried quickly enough to keep the circuitry from peeling or oxidizing. You have to be quick, and remember this above all else: most things you do to any detector will void any warranty in place. This is important. If the warranty is already defunct, meaning it had none, or is past date, then you are ok. With all that taken into consideration, my usual rule is this: learn your tools, it will pay off big in the long run. Its the professional thing to do.
The best way to keep an o-ring seal from leaking is to use silicone grease on the seat and on the o-ring itself. Lather it on generously. Use a Lot.
Heres how: FIRST: clean both the o-ring and the surfaces to be sealed as well as you can. Make sure there is no dirt or grime or grit or Anything there. Do this without fail, every time the o-ring is breached. Then coat the O-ring with silicone grease, sold at most dive shops, and also both surfaces the o-ring will seal with. Use even pressure when reassembling the case, then coat the outer area around the o-ring with silicone grease too. Fill in the cracks, as it were.
This is a mess, and the stuff stinx 4 sure, but it is nothing like the headache you will encounter if the detector leaks. Take my word for it.
Fortunately my detectors are all Whites, and they took good care of me after I had that third leak, which bubbled the printed circuitry right off the board.
I have not had a leak since employing the method above.
I sincerely hope this information prevents many metal detector leaks. Check with your detector manufacturer if you are worried about warranties and the like. Also check out my article below on building a detecting scoop that is very easy to make, inexpensive, and works well in the water and on sand beaches.