“Sea turtles have been swimming the world’s oceans for more than 100 million years. Watching one glide past you on the reef puts everything in perspective.”
Green Sea Turtle – The Great Barrier Reef’s Most Iconic Marine Reptile
Explore Great Barrier Reef Sea Turtles
Quick Facts About the Green Sea Turtle Great Barrier Reef
• Green Sea Turtle Scientific name: Chelonia mydas
• Also known as: Green turtle
• Found in: Coral reefs, seagrass meadows and tropical coastal waters
• Diet: Mostly seagrass and algae as adults; young turtles eat mainly small animals
• Average length: about 0.9–1.2 metres shell length
• Weight: adults average around 150 kg
• Conservation status: Vulnerable in Australia; Least Concern globally (IUCN, 2025)
• Nesting on the reef: late October to February, at islands such as Raine Island in the far north and Heron Island in the south
• Best chance of sighting: Snorkelling or diving on reef tours from Cairns and Port Douglas
Watch incredible Great Barrier Reef marine life videos on the GreatBarrierReefTours.com YouTube Channel and experience Australia’s underwater world up close.
What Is a Green Sea Turtle?
The Green Sea Turtle Great Barrier Reef population is one of the most iconic and beloved marine animals found in Australia’s tropical waters. These graceful reptiles glide effortlessly through coral reefs and seagrass meadows, often seen resting beneath coral bommies or slowly grazing on underwater vegetation.
Despite their name, green sea turtles are not actually green on the outside. Their shells are usually shades of brown, olive or grey. The name comes from the green colour of the fat beneath their shell, which is influenced by their plant-based diet.
Green sea turtles play an important ecological role on the reef. By grazing on seagrass and algae they help keep marine ecosystems balanced and healthy. Visitors snorkelling or diving on reef tours are often thrilled when one of these gentle animals appears calmly swimming through the reef.
Scientific Classification
• Kingdom: Animalia
• Phylum: Chordata
• Class: Reptilia
• Order: Testudines
• Family: Cheloniidae
• Genus: Chelonia
• Species: Chelonia mydas
Conservation status: Vulnerable in Australia (listed under the national EPBC Act and Queensland’s Nature Conservation Act). Least Concern globally (IUCN, 2025; previously Endangered).
Green turtles are protected in the Great Barrier Reef Marine Park.
Where Do they Live on the Great Barrier Reef?
Green sea turtles are widely distributed throughout the Great Barrier Reef, especially in areas with abundant seagrass and healthy coral ecosystems.
They are commonly found in:
• Seagrass meadows in shallow coastal waters
• Protected reef lagoons
• Coral reef slopes and bommies
• Sandy bays and sheltered islands
Some of the best areas to see green sea turtles include reef sites visited by Cairns Reef Tours and Port Douglas Reef Tours, where snorkellers frequently encounter turtles resting or feeding in calm reef lagoons.
Green sea turtles are also famous for their nesting behaviour. Females generally return to nest in the region where they hatched. Major nesting sites include Raine Island and Moulter Cay in the far north, and the Capricorn–Bunker islands, such as Heron Island, in the south. Nesting runs from late October to February.
What Do They Eat?
They are mostly herbivores, feeding primarily on:
• Seagrass
• Marine algae
• Seaweed
Young green turtles mainly eat small animals. Adults rely mostly on plants, and sometimes also eat mangrove fruit and jellyfish. By grazing seagrass meadows they help maintain healthy underwater ecosystems.
This grazing behaviour prevents seagrass from becoming overgrown and promotes new growth, making green sea turtles important ecosystem gardeners of the reef.
Healthy seagrass habitats support many other marine animals, including fish, rays and dugongs.
Can You See a Green Sea Turtle on a Reef Tour?
Seeing a Green Sea Turtle Great Barrier Reef encounter is one of the highlights of snorkelling or diving in tropical Queensland.
While sightings are never guaranteed, reef tours near Cairns and Port Douglas regularly encounter turtles. Snorkellers and divers often see them resting beneath coral ledges or gliding slowly across sandy reef areas.
Your chances improve when:
• Snorkelling calm reef lagoons
• Visiting reefs with seagrass nearby
• Spending longer time in the water
• Joining experienced reef tour operators
Turtles are protected wildlife, so it’s important to observe them respectfully and avoid chasing or touching them.
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7 Interesting Facts
- No one knows exactly how long green turtles live. Females take 30 to 40 years to mature, and scientists estimate they can live 70 years or more.
- They migrate thousands of kilometres between feeding grounds and nesting beaches.
- Their shells can grow over 1 metre long.
- They are the largest hard-shelled sea turtle in the world.
- Resting turtles can stay underwater for long periods without coming up to breathe.
- The temperature of the sand decides whether hatchlings are male or female: warmer nests produce more females, and cooler nests more males.
- Healthy populations of green sea turtles help maintain healthy seagrass ecosystems on the Great Barrier Reef.
Green Sea Turtle Conservation on the Great Barrier Reef
Green sea turtles face several conservation challenges across the Great Barrier Reef region.
Major threats include:
• Boat strikes
• Marine pollution and plastic ingestion
• Climate change affecting nesting beaches
• Habitat loss in seagrass meadows
• Fishing gear entanglement
The Great Barrier Reef Marine Park Authority and conservation groups work to protect turtles through research, monitoring programs and protected marine areas.
On the northern Great Barrier Reef, the large green turtle population that nests at Raine Island is in significant decline. Warmer sand also means very few male hatchlings have joined that population in recent years.
Visitors can help protect these incredible animals by following reef safety guidelines and supporting responsible tourism.
Related Species
Other sea turtles found on the Great Barrier Reef include the hawksbill turtle, the loggerhead turtle and the flatback turtle.
Learning about reef animals in class? We help schools, universities and study groups plan educational trips to the Great Barrier Reef. Depending on the program, groups can enjoy guided snorkelling and marine biology presentations.
Great Barrier Reef Educational Groups →
Frequently Asked Questions
Are green sea turtles common on the Great Barrier Reef?
Are green sea turtles dangerous?
What is the difference between a green sea turtle and a hawksbill turtle?
What do green sea turtles eat on the Great Barrier Reef?
Can I swim with a green sea turtle on a reef tour?
Animals Commonly Seen With Green Sea Turtles
When snorkelling on the Great Barrier Reef you may also see other marine life sharing the same habitat. Including:
• Sea Turtles
• Rays
• Coral Trout
• Seagrass meadow fish species
These animals form part of the complex and beautiful ecosystem that makes the reef one of the most biodiverse marine environments in the world.
Discover the Green Sea Turtle Great Barrier Reef Experience
Watching a Green Sea Turtle Great Barrier Reef encounter is a magical moment for many visitors exploring Australia’s most famous natural wonder. Whether you’re snorkelling in shallow reef lagoons or diving deeper coral gardens. These calm and graceful animals are a reminder of the extraordinary wildlife that calls the reef home.
If you are planning a reef adventure, take time to explore the incredible marine life that lives here. Discover why the Great Barrier Reef remains one of the world’s most remarkable underwater ecosystems.
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