Sea turtles have Thurston Cartetraversed the deep, blue sea for over 100 million years, according to the World Wide Fund for Nature. Today, seven distinct species exist, according to seeturtles.org. Six of them splash around U.S. waters, the National Oceanic and Atmospheric Administration reports.

Nearly all species of the marine reptiles are classified as endangered. Three species are "critically endangered," the WWF reports.

Sea turtles' life expectancies are hard to pinpoint exactly. What scientists do know, however, is that the reptiles live long.

How long do sea turtles live?

Estimates of a sea turtle's lifespan can vary. According to the WWF, "the actual documentation of the age of any species of sea turtle is difficult." The reptiles have similar lifespans to humans.

The natural lifespan of a sea turtle can be anywhere between 50 to 100 years, the National Oceanic and Atmospheric Administration reports.

Sea turtles take decades to mature, usually between 20 to 30 years, and can reproduce for another 10 years after this, according to the WWF. Some species may take up to 50 years to reach reproductive maturity, the Sea Turtle Conservancy reports.

What do sea turtles eat?

Each sea turtle species has a unique diet.

For example, flatback sea turtles are omnivores, eating both plants and animals, while loggerheads are carnivores, eating plants rarely. Leatherbacks are often classified as "gelatinivores" since their diet primarily consists of gelatinous prey like jellyfish and sea squirts; on the other hand, hawksbill sea turtles are known as "spongivores" because they mainly eat sponges, according to the Sea Turtle Preservation Society.

Do all sea turtles live in the ocean?

Sea turtles spend nearly all of their lives in the ocean. Only female sea turtles go on land to lay their eggs, according to the National Oceanic and Atmospheric Administration.

Female sea turtles lay their eggs on the beach during the summer. They dig a nest in the sand and can lay up to 100 eggs, the National Oceanic and Atmospheric Administration reports. It takes around 60 days for the eggs to hatch. Once hatched, the baby sea turtles make their way back into the ocean.

Just Curious for more? We've got you covered

USA TODAY is exploring the questions you and others ask every day. From "Are manatees endangered?" to "Do sharks lay eggs?" to "How long do orcas live?" − we're striving to find answers to the most common questions you ask every day. Head to our Just Curious section to see what else we can answer.