Green sea turtles have been in existence for 250 million years.
They live in the waters of the Hawaiian Islands. After becoming almost extinct because of over hunting, the turtles were tracked. It  was determined that only 67 nesting females remained in 1973. The U.S. Fish and Wildlife Service put them on the Endangered Species List. 

Currently, while being protected, the green sea turtle population grew to more than 800 nesting females. They are now listed as least concern which means they are not considered at risk.
Source: 12 Marine Animals Back from the Brink                by Nancy Furstinger