Alternatives, Sinai, Egypt. Nikon F100, 17-35 mm Nikkor (zoomed through full range), 50 CC Red filter (depth = 4.1 m). On f22, aperture priority - exposure time approx. 1/4 to 1/2 sec. Kodak Elitechrome Extra Colour 100. In general, I got my best results by zooming from wide to short focal