Giant blue hole discovered: Humans are not capable of exploring yet!
The Taam Ja' blue hole is at least 420 meters below sea level and may be connected to a system of hidden caves and tunnels.The green hole is 20 meters deep off Australia
A group of scientists scouted a rare deep blue hole (Blue Hole) in the Great Barrier Reef. This green hole is located more than 200 km from Daydream island off northeast