Since no one has started a thread on waterproof cases for iPhone 4, I have taken the liberty to create this thread dedicated just for it.
Here's what I have found so far.
Will update along the way when I find more. All are welcome to chip in as well 
1) Lifeproof™
Web: http://www.lifeproof.com/
2) iDry™
Web: http://www.idryworld.com/
3) Innopocket™ Amphibian
Web: http://www.innopocket.com
4) Aquapac™
Web: http://www.aquapac.net/
5) Phone Dome
Web: http://www.designtong.me/xe/whatis_phonedome
6) Dry Case™
Web: http://www.drycase.com/
7) Dry Pak
Web: http://www.drypakcase.com/drypak/
8) H2O Audio™ Amphibx
Web: http://www.h2oaudio.com/
9) DiCAPac™
Web: http://www.dicapacusa.com/default.asp
10) Aqua Box
Web: http://www.aquaboxproducts.com/index.htm
Here's what I have found so far.
1) Lifeproof™
Web: http://www.lifeproof.com/
2) iDry™
Web: http://www.idryworld.com/
3) Innopocket™ Amphibian
Web: http://www.innopocket.com
4) Aquapac™
Web: http://www.aquapac.net/
5) Phone Dome
Web: http://www.designtong.me/xe/whatis_phonedome
6) Dry Case™
Web: http://www.drycase.com/
7) Dry Pak
Web: http://www.drypakcase.com/drypak/
8) H2O Audio™ Amphibx
Web: http://www.h2oaudio.com/
9) DiCAPac™
Web: http://www.dicapacusa.com/default.asp
10) Aqua Box
Web: http://www.aquaboxproducts.com/index.htm
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