Even if the water is really clear, as it was on this dive, it is always best to get as close to the subject as possible when taking photos underwater. To this end I used my 15mm fisheye behind an eight inch dome port on a Canon 5D. The full frame sensor gives you a true 15mm, unlike some of the cropped sensor cameras which enabled me to shoot the entire wreck from fairly close on, hence keeping image quality as high as possible. To get realistic colours, I manually white balanced on the wreck at the depth I was shooting and used a Magic Filter in the rear gelatin filter holder on the 15mm to get better blue colour rendition.
For a few more shots of Sara, you can visit my website.