RE: waterproof omputers Do you mean RC recievers or something else? (you can get RC recievers at pretty much any hobby shop or online) Watertight boxes are either hand built or modified otter boxes or stuff like that. A lot of people have stopped using watertight boxes and use other waterproofing methods.
RE: waterproof omputers Most receivers are easy to remove the case. Either a couple screws or a pair of tabs, etc. If you're not sure, post a few pictures (or the model of the receiver) and we can tell you. Once the case is off, it's a simple matter to paint the receiver with skotchkote or other waterproof coating.
RE: waterproof omputers I just pot the receivers in a block of epoxy, case and all, much easier than removing the case. I put short extensions on all the pins and those get potted in place as well. (this is also handy since I've stopped using standard servo connectors and switched to 3 pin deans for reliability) Simple and effective.
RE: waterproof omputers I had several receivers die in (non)WT boxes (I sucked at that early on), but I did what SnipeHunter described and haven't had a problem since.
RE: waterproof omputers I'm still using WT boxes. The best so far is a converted Pelican box. In the past two years and multiple sinks, it has never leaked. A good article for converting the box is at http://www.modelwarshipcombat.com/howto/DryBoxes/diveboxdrybox.pdf.