Undersea penetration by ambient light, and visibility.
Undersea observations from various submersibles reveal penetration by ambient light to depths as great as 700 meters. The range of horizontal viewing under ambient light in offshore tropic and subtropic areas varies from 5 to 6 meters (estimated) at 300-meter depth to more than 60 meters at 183-meter depth. Such observations indicate that ambient light may be usable for undersea tasks to greater depths than was anticipated.
D008027:Light; D009791:Oceanography; D014785:Vision, Ocular