Scientists have discovered a sinkhole in the ocean off the South China Sea that they believe to be the deepest ever recorded. This one called the Dragon Hole has been recorded at 300 meters or 987 feet deep. The previous record holder was the Blue Hole in the Bahamas at 202 meters. The hole appears to be self contained and contains over 20 species of fish. The holes appear when carbonate rocks dissolve. This is exactly how sinkholes form, when limestone, which is a carbonate rock, is dissolved away usually by acidic water. People may not know that you can dive sinkholes right here in Florida. One of the more famous ones, Devils Den, is in the Ocala area but there are many others throughout the state.