This trip is gonna rock! If you know anything about D-SLR, I'm preparing for a trip of a lifetime (photos). Any insight is appreciated, otherwise, seatbelts fastened...
SoCalBruin.
Galapagos is more of a video place than a still photo place. Most of the time, you'll want the widest angle lens you can afford. With most D-SLR cameras, the sensor is not quite 35mm, so the net effect is to make lenses longer. So you want a even wider angle lens than with a film 35mm.
I went to Galapagos many years ago with a Nikonos V and a 20mm lens. I'm not a very good photographer, but even though I took about 60 photos of whale sharks, I didn't get one I liked. The problem was that with a 20mm lens to get a good portion of the whale shark into the frame, I had to back away to the point I was out of strobe range. I also had a new strobe and hadn't really figured out how to use it yet.
I've switched to a little digital point and shoot. I like it because I can just tuck it into my cumber bun and forget about it. I don't expect to get many good still pictures of hammer heads and whale sharks, but I will make good use of the video feature. The other great thing about it is that I can take something like 500 photos before I fill the memory card. That means I don't have to open it after every dive, which means less time messing with o-rings.
So my advice is wide angle lens, the biggest memory card and the best batteries you can get. Then just take lots of pictures. Some of them will come out. It looks to me like one of the other people on this trip (sorry, I've forgotten who) really knows his way around a camera and has also been to Galapagos before. I'd PM him and see what hints you can get.
Ross