The special reveals the instincts of territorial sea creatures and their alarming defense mechanisms that harm unsuspecting human swimmers. While often only attacking when provoked, these usually timid creatures can pack a mighty blow. These are the stories of the deadliest blows.

STINGRAYS: The tragic and untimely loss of Steve Irwin brought home the risk of swimming near a stingray. Their poisonous barbed tail can strike a swimmer instantly.

BLUE-RINGED OCTOPUS: The hypnotic colors of the blue-ringed octopus can lure people into the beauty of this mysterious, drifting creature. Behind the beauty lies a deadly bite. Its paralyzing venom is contained in its salivary gland.

BARRIER REEF: Amidst the world’s largest coral reef ecosystem lurk deadly predators. Stomatopods (commonly known as mantis shrimp) are predatory crustaceans. Their raptorial claw can dig deep into a human. The cone shell’s teeth resemble small harpoons. A bite can result in muscle paralysis or death. The box jellyfish can be classified as predator or prey. When in a predatory state, the creature injects its deadly toxins into its victim.

NINGALOO REEF: Lions mane jellyfish, moray eels and sea snakes are all creatures to be feared in Ningaloo Reef, off the coast of Western Australia.

IRUKANDJI JELLYFISH: These jellyfish inhabit Australia’s northern waters. Unlike other jellyfish, the Irukandji jellyfish has stingers not only on its tentacles but also on its bell. Also unique to this jellyfish is that the venom is injected only from the tip of the stinger rather than the entire length.

CROCODILES: When a 4-metre crocodile climbed out of the sea onto a beach in far North Queensland beach, grandmother Alicia Sorohan wrestled the croc as it dragged a family friend into the water.

SHARKS: Divers Rodney Fox and Ben Cropp show how they survived attacks by deadly sharks.