I need a waterproof case for a DSLR with two lenses and some misc extras. I'm familiar with Pelican cases and might go that route. I need something that can be submersed in water and will float. Are there any good alternatives?
I've used three options, and I trust them all.
The most important thing in choosing a waterproof case is that you know it works. Before putting your gear in the Pelican case or drybag, fill it with some tissues or toilet paper because they're super absorbent. Seal the box/bag, and put it in your bathtub and completely submerge it. Hold it under. Bounce it around. Make sure you try to work the water in. Leave it in there for a while -- maybe even an hour -- to see if any water can work its way in. Finally, pull the case/bag out, open it up, and verify that the toilet paper is still dry.
Presumably, you need a waterproof option because you're going to be in a boat. A tip: use a line to tie your case or bag to your boat. If you do capsize, you don't want to lose the gear because it floated away faster than you could get to it. With a length of rope, you can just pull your canoe (or whatever) to shore and know that you've got everything still attached.
Sealine offers a good line of Dry Bags
I've used these while camping to provide solid protection in my back pack.