Recent shark attacks in Australia's Sydney Harbor and Bondi Beach are probably due to cleaner waters and an increasing population of fish. The Australian government's efforts to clean up the marine environment have brought many fish species back from the brink of extinction.

Scientists say while it is unclear whether shark populations are actually increasing, cleaner waters have brought the sharks closer to shore to feed on the now healthy fish populations.The Bondi Beach shark attack on a surfer was the first one there since 1929.

Thirty types of sharks,including the Great White,remain on the threatened species list.