Up to 40 cm. Camouflaged perfectly as a rock or coral. 13 dorsal spines deliver venom when stepped on. Most venomous fish in the world.

Sting causes excruciating pain (described as the worst pain known to humans), tissue death, paralysis, heart failure. Antivenom exists; ~25 cases per year in Australia. Few deaths now.

Tropical reefs and rocky shores of northern Australia, PNG, Indonesia, Philippines, Fiji, all tropical Indo-Pacific.

Almost motionless — relies entirely on camouflage. Buries partially in sand. Most stings: tourists wading without reef shoes.

Beautiful patterned shell 10-15 cm long. The most venomous of all cone snails. Hunts fish with a venomous harpoon-like tooth fired from a proboscis.

Conotoxin causes total paralysis with no antidote — mortality ~30%. Victims describe being conscious but unable to move or breathe. Patients survived by being put on ventilators until toxin cleared.

Coral reefs and sandy areas of tropical Indo-Pacific — Australia, PNG, Indonesia, Philippines, all Pacific islands.

Slow-moving but hunts fish (!) by harpooning them with a tooth shot at high speed. Tourists picking up the pretty shell get stung.

Tiny — only 12-20 cm tip-to-tip. Yellow-brown with bright blue rings that pulse vividly when threatened. Looks adorable. Is lethal.

Tetrodotoxin (same as pufferfish) — 1,000x more potent than cyanide. One bite paralyzes adults; victim conscious but can't breathe. No antivenom. Treatment: artificial respiration for 24+ hours until toxin clears.

Tide pools and coral reefs of Australia, Papua New Guinea, Indonesia, Philippines, Solomon Islands.

Hides in shells, bottles, debris. Bite is painless — victim may not realize until paralysis begins minutes later. Picked up by tourists curious about color.

Black above, bright yellow below, paddle-shaped tail. Up to 1 m. The most widespread snake in the world — Indo-Pacific from Africa to Americas.

Highly potent neurotoxin — 10x more toxic than cobra. But docile and rarely bites swimmers. Most bites: fishermen entangled in nets.

Open ocean throughout Indo-Pacific — Australia, all Oceania islands, Indonesia, Philippines, India, even Pacific coast of Mexico/Central America.

Fully aquatic — cannot move well on land. Drinks fresh water from surface rain layer. Floats among debris hunting small fish.

Up to 5 m with vertical tiger-like stripes (fade with age). Eats almost anything — license plates, tires, and human remains have been found in their stomachs.

Second only to great white in unprovoked human attacks. Common in Caribbean and Hawaiian waters. Slow but powerful — strikes once and waits.

Tropical and subtropical waters — Florida, Caribbean, Gulf of Mexico, Hawaii.

Solitary, mostly nocturnal. Migrates long distances. Females birth up to 80 live pups.

Not a jellyfish but a colony. Distinctive blue-purple gas float with 30-metre tentacles trailing below. Drifts onto US Atlantic and Gulf coasts.

Excruciatingly painful sting causing whip-like welts. Rarely lethal, but several deaths recorded from heart failure or drowning after shock.

Atlantic and Gulf coasts — Florida, Texas, Louisiana, North Carolina; sometimes washes up by the thousands.

Drifts on wind via sail-like float. Cannot swim — entirely passive. Tentacles sting for weeks even after death.