This is a very weird looking creature. When scared, they inflate themselves with water to look bigger, but can die from stress. This one was swimming happily next to a coral pillar and I managed to get really close without spooking it. I managed a few pictures before having to catch up with my speedy guide again.
Nikon D700, Nikon 28-105 mm macro at 105mm, F8, 1/60th, ISO 400, Ikelite Housing and Ikelite DS160 strobe set on TTL.
Temple, about 18 metres down, Sharm El Sheikh, Egypt.