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Portsea Hole
The Portsea Hole is a depression in the seafloor of Port Phillip near Portsea in Victoria, Australia. The undefined area of the depression, generally assessed at , is one of six separate areas that comprise the Port Phillip Heads Marine National Park and is a popular site for divers. Features The Portsea Hole is a remnant section of the drowned valley of the Yarra River, descending sharply from the depth of the surrounding seabed to , exposing changes in the strata of the limestone sides with depth. It is characterized by diverse and abundant fish assemblages as well as a rich benthic community of marine invertebrates, encrusting algae, sponges and soft corals. The Portsea Hole in Port Phillip is about from the Portsea Pier. To the north there is a vertical wall approximately long. The wall has small overhangs which are home to plenty of marine life, including Blue Devil fish. The Portsea Hole is a popular boat dive site for recreational scuba diving Scuba diving is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Hole
A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock (limestone or coral reef). Their existence was discovered in the late 20th century by fishermen and recreational divers. Blue holes typically contain tidally influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages. Well-known examples are the Dragon Hole (in the South China Sea) and, in the Caribbean, the Great Blue Hole and Dean's Blue Hole. ''Blue holes'' are distinguished from ''cenotes'' in that the latter are inland voids usually containing fresh groundwater rather than seawater. Description Blue holes are roughly circular, steep-walled depressions, and so named for the dramatic contrast between the dark blue, deep waters of their depths and the lighter blue of the shallows around them. Their water circulation is poor, and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
