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Without the search feature, I have no recourse but to ask and hope someone will help.


I see there are many recommended waterproof containers listed on the forums. I so far have ammo cans but I am wondering…. are they reliable for full time submersion?


I want to create a cache that will live underwater. Can anyone verify if ammo cans (gasket greased good) will hold up to the task or something else? It also must sink and not float and a lot of fancy plastic waterproof containers look like they are designed to float plus they are bright colors. I want mine to sink like a stone and blend and I doubt paint on plastic would hold up under water so I’m hoping someone can verify the ammo can will do the job! I need to be able to attach a rope to it too so it has to have a handle or something.


Thank you so much for any help you can give me! :laughing:

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Containers designed for scuba use - there are battery canisters of various sizes for underwater lights, will stay dry. However, all such containers are relatively pricey and require some considerable care in working the closure.

The gaskets need to be perfectly clean, something that's easy for a diver, tough for a geocacher, who typically has pulled it up out of the muck and may not have a supply of clean water for rinsing the opening and gasket.

That said, I have a large stainless scuba battery canister out, good so far.

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A geocacher here in the Atlanta area (Trez003) has used an ammo box for a submerged cache and it remained watertight at a depth of a few feet for months. He reported that the biggest problem was algae growth on the can ... it got slimy. I don't think every ammo can is that watertight, the seal has to be perfect. Another cacher used a piece of PVC with a pipe threaded plug, but that one was wet when I found it. The problem with that approach is that if you tighten the plug tight enough to seal, a wrench may be needed to remove it. Another submerged cache used a glass jar with a sealing cap (like pickles and maracino cherries come in) and weighted it so it would not float. I don't know if this proved to be watertight at depth.


FWIW, CharlieP

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I am using a 30cal ammo can ballasted with a brick. So far so good. I tested the seal for several days prior to placing the cache. I haven't used any grease or sealer other than the gasket it came with. The cache lives in the river with a fair to moderate current.

Reports thus far are the contents are dry while the outside has a slimey feel to it.

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Many containers containers will work for a time, but most watertight containers are designed to protect the contents for hours, not weeks or months. Even if you find a container that will keep everything dry you still have to trust the finders to close it correctly.


So no matter what container you choose, assume the contents will get wet eventually. That means you should make your log out of waterproof writing paper (National Geographic Adventure Paper is the best I've found) and only place contents that will not be ruined if they get wet. Coins for example.

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Just another thought... what if the submerged cache was the first stage of a short multi? You could then sink something clear with a laminated card with the coords to the final on it to a nearby ammo can.


That way even if stage 1 does leak, no big deal. But they still have to this sub-surface to find it :laughing:

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As a follow up to WIsearcher's question:


What are some ideas for hiding an underwater cache, particularly in somewhat shallow water, say waist high? There is a very nice bay near where I live and I thought it would be a great location for a cache. Thanks for the help.

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One solution I've seen for keeping a potentially submerged container dry inside is to stand it up in another container with the seal at the top. Even if some water gets in the other container, it's unlikely to rise to the level of the seal on the inner container. The water gets emptied out every time someone finds the cache or you do a maintenance run. I've seen this technique used with a bison capsule inside a pill bottle. I'm not sure how you would do it with an ammo can. You can't get a .30 cal box inside a .50 cal box and those are the two readily available. But there are other types of containers available at surplus and sporting goods stores that might work.

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In Wisconsin there are a couple submerged caches. At this time, I think only one is surviving (Rock Lobster). It's a Nalgene bottle. But with any underwater cache, it should get frequent maintenance checks.


Also, depending on the location in WI, remember that it may be frozen in place for a time too.


In WI, a cacher by the name of Prostreet had an underwater cache active for quite some time -- Under Where -- it got a cache of the month award by the WGA.


Also another WI cachering family -- by the name of WISearchers (what are the odds on that?) had a submerged cache. But I can't remember the container. It was small. I remember that the contents were wet though.


I also see by your profile that you live near me -- I'll be looking for your cache!



Edited by greyhounder
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And I've heard there's a great "submersible" for the "final" of Team Geo-Pink's submarine series. It also got a WGA award. I've never been to it, and have only heard bits and pieces about it though (it's one of those caches that you have to do to fully understand the submersible part). It is currently disabled due to weather.



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I found a cache in Ohio that was a 1 gallon Thermos container weighted down with a floor tile at the bottom of a river. It was tied to a tree at the riverside. No one had found it for quite some time before I got there and all the contents were nice and dry.

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I plan on adding a submersible cache to my geo-resume, and my thoughts were originally to just sink an ammo can with a brick. A lot of these have stayed dry, however, it's not 100%. I like the idea of a container inside a container, which effectively doubles your chances that your cache will stay dry. Perhaps a Nalgene bottle inside a Thermos? Double wrap a waterproof logbook, and insist on trade items that can tolerate submersion?


Just thinkin' out loud...

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Ammo Cans (when used for real ammunition) are required to be pressure and leak tested under water. 99.9% of them pass without a problem...it's the .1% that you have to be careful of and usuallly those are because the seal was improperly placed. The thing that I would worry more about with an ammo can in salt water would be the hinged top getting so encrusted (sea life, salt, etc.) that you couldn't open it easily! Isn't there a requirement that you check your cache regularly? As long as you are doing that, it shouldn't be a big problem. Test it first a couple of times with a roll of toilet paper in it to see if you pick up any moisture. If not, you should have a good can to work with.



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If you have a dive shop near you, they have plastic boxes in many sizes by Pelican that are used by divers to store stuff and keep it dry. Here is the sales pitch from Cases by Pelican :


Pelican Case ® built to protect in the most severe conditions:


Lightweight space-age resin: ultra high impact structural copolymer polypropylene, provides 4 times the strength to weight ratio over conventional injection molding, unaffected by dents, scratches or corrosion. Pelican Case meet MIL-STD 4150-J stacking (400 lbs.) Drop Test (48"), Immersion (2" at 160°F). They meet and far exceed the highest standards of industrial, airline, military and commercial applications.


Multiple massive ABS Latches and .250 neoprene closed cell "O Ring" , provides up to 30 feet watertight and air tightness for the ultimate protection.


They have all sorts of shapes, sizes, colors, and some even have clear lids.



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