Sea Turtles: Ancient Mariners of the Reef

Living Fossils

Sea turtles have existed in approximately their current form for 110 million years — they were navigating the oceans while dinosaurs still walked the continents. The seven living species (green, hawksbill, loggerhead, flatback, olive ridley, Kemp's ridley, and leatherback) have survived five mass extinctions. They are now in trouble from human activity on a timescale of decades.

For divers, sea turtles are one of the most reliably encountered large animals across tropical dive sites worldwide. They are unhurried, habitually indifferent to divers who approach quietly, and genuinely beautiful — the curve of the shell, the slow pull of the flippers, the upward angle of their surfacing to breathe.

The Two Species Divers Most Often See

Green sea turtle (Chelonia mydas) is the most commonly encountered species on reefs worldwide. Adults are herbivores (grazing on seagrass and algae), which gives their flesh its distinctive colour. They sleep in caves and crevices on the reef, and divers frequently encounter them resting motionless on the bottom. On feeding grounds, they can be watched grazing for extended periods at close range.

Hawksbill sea turtle (Eretmochelys imbricata) is narrower-headed, more pointed-beaked, and typically found on reef walls and coral structures (not open seagrass beds). They feed predominantly on sponges — which most other marine animals cannot digest due to their silicate spicule content — making them an important reef ecological player. The spectacular layered shell pattern of hawksbills has made them the most poached for shell trade.

Best Turtle Encounters Worldwide

• Sipadan Island, Malaysia: Green and hawksbill turtles in extraordinary concentrations — you will see more turtles on one Sipadan dive than on entire dive trips elsewhere. They breed in the island's famous 'turtle cavern' (overhead environment; expert-only).
• Apo Island, Philippines: A community-managed marine reserve; turtle population has recovered dramatically since protection began in 1982. Multiple turtles on every dive.
• Akumal, Mexico: A bay on the Yucatán Caribbean coast where green turtles feed on seagrass; snorkel encounters year-round
• Ningaloo Reef, Western Australia: Loggerhead and green turtle nesting beach; snorkel and dive encounters abundant
• Ras Mohammed, Sinai (Egypt): Hawksbills on the walls; green turtles on the reef flat

Approach Protocol

• Do not touch. This point is worth making firmly: touching a turtle interrupts feeding or rest, transmits pathogens, can remove protective skin oils, and is illegal in many jurisdictions.
• Approach from the side or front, not from above or behind. Coming from above mimics a predator.
• Move slowly and stop several metres away. A calm turtle will often continue what it is doing; an approached turtle that is disturbed will leave.
• Do not position yourself between a turtle and the surface — they must breathe regularly, and blocking their ascent path causes significant stress.
• Never ride. This is obvious and yet still occurs. It is harmful, distressing to the animal, and illegal at most dive sites.

Conservation

All seven sea turtle species are classified as Vulnerable, Endangered, or Critically Endangered. Primary threats include bycatch (entanglement in fishing nets and longline hooks), egg poaching (turtle eggs are considered a delicacy in parts of Southeast Asia and Latin America), coastal development (nesting beach loss), plastic ingestion (sea turtles mistake plastic bags for jellyfish), and boat strikes.