Contrast in the extreme

This is a water cave or passageway from one large body of water to another in Ha Long Bat, Vietnam, and it was a real challenge in terms of exposure.  The wider the angle lens, the more of the dark recessess of the rock formation were included in the picture.  That meant that the meter would be influenced by all of the darkness, thus overexposing the sunny areas.  A narrower angle lens would provide an accurate exposure but it would eliminate most of the cave.  I chose a 14mm wide angle for the extensive depth of field, but I had to wait until I was positioned near the opening to include the right amount of the rock ceiling plus the opening scene.  Since this was taken from a boat which was constantly moving, I had seconds to make a determination of the composition and the exposure.  Plus, there were many other boats that I had to eliminate from the shot.  It was indeed a challenge, and I got only one good shot.  My settings were 1/400th of a second, f/10, and 1000 ISO.