<P> Sea turtles are generally found in the waters over continental shelves . During the first three to five years of life, sea turtles spend most of their time in the pelagic zone floating in seaweed mats . Green sea turtles in particular are often found in Sargassum mats, in which they find shelter and food . Once the sea turtle has reached adulthood it moves closer to the shore . Females will come ashore to lay their eggs on sandy beaches during the nesting season . </P> <P> The habitat of a sea turtle has a significant influence on its morphology . Sea turtles are able to grow so large because of the immense size of their habitat: the ocean . The reason that sea turtles are much bigger than land tortoises and freshwater turtles is directly correlated with the vastness of the ocean, and the fact that they travel such far distances, especially the leatherback sea turtles . Having more room to live enables more room for growth . </P> <P> It takes decades for sea turtles to reach sexual maturity . Mature turtles may migrate thousands of miles to reach breeding sites . After mating at sea, adult female sea turtles return to land to lay their eggs . Different species of sea turtles exhibit various levels of philopatry . In the extreme case, females return to the beach where they hatched . This can take place every two to four years in maturity . </P> <P> The mature nesting female hauls herself onto the beach, nearly always at night, and finds suitable sand in which to create a nest . Using her hind flippers, she digs a circular hole 40 to 50 centimetres (16 to 20 in) deep . After the hole is dug, the female then starts filling the nest with her clutch of soft - shelled eggs . Depending on the species, a typical clutch may contain 50--350 eggs . After laying, she re-fills the nest with sand, re-sculpting and smoothing the surface, and then camouflaging the nest with vegetation until it is relatively undetectable visually . The whole process takes thirty to sixty minutes . She then returns to the ocean, leaving the eggs untended . </P>

How many years until a sea turtle comes back to lay eggs