In 1998, I decided to combine my interest in photography with one of my newer interests - scuba diving. I researched underwater cameras and housings, and decided to go with a housed SLR. Underwater viewfinder cameras such as the Nikonos V are ideal for wide angle photography, but macro becomes very difficult because focusing has to be precise and parallax distortion becomes very significant at close distances. Most Nikonos user's resort to framers when taking macro shots, which are impractical for many underwater subjects.
The housed SLR has all the advantages of an SLR above the water, although a housed camera is relatively big and heavy, particularly compared to cameras such as the Nikonos. SLR housings have separate ports (housings for the lens that screw into the housing for the body) for each different kind of lens. If you want to take wide angle shots, you need a large done port in order to provide the angle of view necessary with minimal distortion. All these components add up to a lot of gear. On my last diving vacation, I ended up with a medium size Pelican case just for the underwater housing and strobes.
Unfortunately, I was not able to find a housing that I liked for the Canon A2E. The Nikon N90S seems to be the most popular camera for this application - there are several quality housings available. So, I invested in a Nikon setup (N90S, 20mm, 28mm, 60mm macro, 105mm macro) - my comments on Nikon vs. Canon below. I decided to purchase the Sea & Sea NX90 housing after taking a trip to talk to Geoff Semorile at CameraTech in San Francisco. I bought a standard macro port, a port extender (to extend the macro port to fit the 105mm lens), a dome port (for the 20mm lens), and two Ikelite 50 strobes on extender brackets. Geoff convinced me that two strobes will always be preferable to one, and that two small strobes will be satisfactory for most applications and are a lot easier to manage and travel with than their larger relatives. So far, I think I made the right choice.
I used the housing on a scuba diving vacation (to Bonaire) and I'm very pleased with the performance of the housing and the results I attained. While I've still got LOTS to learn, I didn't think my first results would as good as they were.
A great website to learn about underwater photography equipment and see some great photo's is Bjorn Jensen's website.