This is the first color photograph ever taken underwater. It’s a hogfish captured off the Florida Keys in 1926 by National Geographic photographer Charles Martin and Dr. William Longley. In addition to some special waterproof camera housing, the duo used pounds of highly explosive magnesium flash powder to illuminate the scene.
The powder was actually in a raft on the surface of the water. When they pressed the camera shutter, it tripped a battery on the raft, which triggered a powerful explosion that illuminated the underwater scene up to 15 feet deep.
Camera flashes have come a long way since then, huh?