I also have not tried it, but was thinking something like silicone sealer, or maybe a type of glue that remains flexible when dry. There used to be a product called "Shoe Goo" that could be used in this way. You would want to test it first on something small, perhaps make a little bag, seal up all the seams and then when it's dry fill it with water and see what happens. Have now Googled - voila: http://www.rei.com/product/679240/so...9-001b2166c2c0

Of course, by the time you buy enough of this kind of product plus your other materials you might have spent more than on a ready made bag, and your time is worth something.

I have made them for my grandkids to place wet bathing suits in after swimming...I used a shower curtain and use clips to hold it together instead of pins while sewing...also I put in a polyester zipper..that way zip open put in wet stuff zip closed...no mess in the car on the way home...also good for small toddlers who are potty training and have an accident..easy clean up...good luck with your project.

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> I replaced the plastic windows on my son’s boat. I could not pin the fabric, however this tape called seamstick I used holds it in place to sew, I don’t think it will allow water in, it did not on the boat. I used Sunbrella fafric.
http://search.sailrite.com/?freeText=seam%20tape&history=p6defdi5||sub_attr_n ame~Store_ID^refineValue~Retail1...ewdl17r6||categ oryName~cat_121353%40Retail1^category~121383%40Ret ail1^subCategoryName~Notions^subCategoryName~Notio ns
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If you wanted to try a quick bag and go to a camp shop and buy a can of canvas waterproofing.

See if you can find an umbrella tutorial on utube or here. If we can make seams in an umbrella that don't leak, you should be able to use them in a bag. Right?

There are special seam sealers and seam tapes sold in camping stores. I echo the folks recommending something like a Lock and Lock or Pelican sturdy plastic container for protection of valuables, then making a bag to hold them. I used to scuba and no matter how careful I was something eventually got wet through leakage. You can make small tightly woven cloth bags of silica (from drying flowers kits) or reuse the silica bead packets that come with new shoes and purses to keep the humidity down so you won't get rust or molding in sealed containers. Just velcro them into the container and replace them frequently. This works even in a home safe.

Wow - lots of neat suggestions. I appreciate all of them. Thank you! The plastic containers sound like a neat idea. DH looked at the website posted (www.thewaterproofstore.com) and found a duffle bag he liked for strapping to the trunk of the bike incase we take an overnight trip on it.

Will post pictures of what I make.