You have many options actually.
Go Pro makes a nice camera and has by far the largest market share. A flat lens is a must with these. The GoPro housing is the least expensive at $49 for a full replacement housing. Backscatter is building a flip up red filter for GoPro to sell, but I am not sure when that will be on the market. If you are looking to spend less, Mako makes a replacement lens that you can install yourself.
Other options on housings include the Backscatter, SRP, and Eye Of Mine.
Backscatter Custom GoPro Underwater Housing with Glass Lens and Removable Filter Mount
BlurFix
Eye Of Mine Homepage
If you want to go REALLY deep, Sartek makes a housing that can do it.
Sartek Industries Product Details
All have their pro's and con's. I own all of them, aside from the Sartek. My personal favorite is the BackScatter due to its ability to change filters underwater.
Another option you can look in to is the Intova Sport HD. It has a lot of the features that Go Pro left off. LCD screen, flat lens, zoom, and user adjustable white balance. This takes good pictures and video, but does not have some of the same options on video like the GoPro. It does not allow for adjustable Fields of View, nor does it shoot in 60 frames per second. It is however at a very affordable price point, coming in at just under $200.
Sport HD | Intova
Shameless plug. A video I shot is at the bottom of this link.
I own 2 Go Pro's and an Intova. I like all of them for different reasons.
Another option is mentioned above. The Contour. I have not used one underwater, but have used them for sparingly for motorsports, and they work well.
Contour | Products | Contour Roam
Yet another option is from Sartek. They put out a camera very similar to the Intova.
Sartek Industries Product Details
Hope this helps in some way.