Meet the Sea Snakes with Incredibly Lethal Venom

Fun Facts About Sea Snakes

• Although they evolved from terrestrial ancestors, the vast majority of sea snakes cannot move on land.
• Sea snakes can move both forward and backward in the water with equal speed and dive as deep as 328 feet.
• As water-dwelling air breathers, sea snakes must come up to the surface to breathe every two hours.
• Although highly venomous, sea snakes are not usually aggressive. Most species’ fangs are not long enough to penetrate a wetsuit.
• Most bites occur when fishermen are removing the sea snakes from nets or when the snake is stepped on in shallow water.

Most Sea Snakes Dwell in Shallow Waters

Despite their marine adaptations, most sea snakes prefer to inhabit shallow waters near land, around islands, and in sheltered waters. Closely related to the Australian venomous terrestrial snakes in the family Elapidae, Sea snakes are classified into two broad subfamilies. True sea snakes (subfamily Hydrophiinae) and the more primitive sea kraits (subfamily Laticudinae).

Sea Snakes Have the Most Potent Venom on Earth

The majority of adult sea snake species grow to be between 4 feet and 5 feet in length. The largest sea snake, Hydrophis spiralis, reaches a maximum length of 10 ft (3m) – one of the largest snake species in the world! Sea snakes have the most potent venom of all snakes in the world. Though the majority of sea snake species have gentle dispositions, some aggressive sea snake species are more irritable and capable of killing an adult human in less than 30 minutes. 

1. Yellow Sea Snake

Hydrophis spiralis, the yellow sea snake is the longest species of sea snake in the world, growing up to 3.0 meters long (up to 10 feet!) It is commonly seen in the Indo-Pacific, especially the northern Indian Ocean and Southeast Asia. As its name implies, the yellow sea snake’s color is yellowish or yellowish-green above but the dorsal scales are edged with black. In the young Hydrophis spiralis, the head is black with a yellow horseshoe-shaped marking, but the head is usually completely yellow in the adult. Compared to most sea snakes, the venom of the yellow sea snake is usually less toxic and less copious. It feeds primarily on eels and is found in muddy, sandy ocean bottoms.

2. Stokes’s Sea Snake

Hydrophis stokesii, Stokes’s sea snake, is a large species of sea snake in the family Elapidae. Located in the tropical coastal areas in the Arabian Sea, the Taiwan Strait, and northern Australia, Stokes’s sea snake is one of the largest species of sea snake in the world. Reaching a total length of up to 5 feet, and some individuals even measuring up to 6 feet, this species is one of the heaviest and bulkiest sea snakes in the world. They often vary in color, ranging from cream to grey to brown to black, with broad black dorsal crossbands. With fangs long enough to pierce a wetsuit, this robust sea snake has the longest fangs of any marine snake.

3. Olive Sea Snake

Aipysurus laevis, an olive sea snake, has brownish and purple scales along the top of its body while its underside is white. It is a large venomous sea snake species measuring about 3.2 feet, with some individuals growing to be about 6.4 feet (2m).

The olive sea snake usually hunts in coral reef areas, using its special photoreceptor organs to remain completely hidden in the dark, safe from predators. Apart from its remarkable size, the sea snake species is highly venomous, and it hunts small crustaceans, fishes, and benthic invertebrates, including prawns and crabs. Found in the shallow waters of the Indian Ocean, Western Pacific Ocean, and parts of Northern Australia, it spends its entire life cycle in the ocean.

4. Yellow-lipped Sea Krait

Found in the tropical waters near the Indian Ocean and Western Pacific, the yellow-lipped sea krait (Laticauda colubrina) is a species of highly venomous sea snake from the Elapidae family. The yellow-lipped sea krait has a characteristic yellow snout (hence its name) and distinct black stripes with a paddle-shaped tail for swimming. On average, the body length of the yellow-lipped sea krait totals about 3 feet to 6 feet at maturity, one of the longest for a sea snake species. Females are significantly larger than males, with an average total length of 1.42 m (4 ft 8 in).

Although they spend much of their time in the water, they can also return to land to digest, rest, and reproduce. They often encounter humans on land but they’re not aggressive, only attacking when provoked. The venom of Laticauda colubrina is highly toxic, and it uses to prey on eels and small fishes.

5. Zweifel’s Beaked Sea Snake

The Zweifel’s beaked sea snake (Enhydrina zweifeli), also known as Sepik beaked sea snake, is an uncommon species of sea snake. It has a gray to brown body discoloration, a rounded snout, a notch at the jaws, and light-colored transverse bands that taper along the body. It can grow up to nearly 5 feet in total length, making it one of the largest sea snakes in the world. Commonly found in the temperate waters of Papua New Guinea and the Australian Coast, the Zweifel’s beaked sea snake feeds on smaller fish but occasionally preys on large fish such as catfish. They’re highly venomous and aggressive, reportedly known to bite under slight provocation.

6. Beaked Sea Snake

Enhydrina schistosa, the beaked sea snake (otherwise known as hook-nosed sea snake) is among the most venomous sea snakes. The snake is usually uniformly dark grey above; the sides and lower parts are whitish. An adult beaked sea snake grows up to an average length of 4 feet, while some larger specimens may be as large as 5.1 feet. They are highly venomous and notably aggressive, responsible for more than 50% of all bites caused by sea snakes and up to 90% of deaths from sea snake bites each year.

This deadly snake is usually found in the Arabian Sea, the Persian Gulf, and parts of Southeast Asia (especially on the coast and coastal islands of India). The beaked sea snake can dive into deeper waters up to 100 m and stay underwater for hours to hunt for prey. Their primary source of food is fish.

7. Dubois’s Sea Snake

Another highly venomous species of sea snake, Aipysurus duboisii is known as Dubois’ sea snake or reef shallows sea snake. Its venom is one of the most potent in the world, making it one of the leading most venomous snakes in the world – they can cause life-threatening envenomation; urgent treatment is essential. They are endemic to the coastal waters of Southeast Asia and Australia. Adults grow up to about 2.6 ft to 4.8 ft in body length and they are easily identified by their smooth dorsal scales, long fin-like tails, wide head, and series of dark brown crossbands on the skin. Living in depths of up to 262 feet (80 meters), Dubois’ sea snakes feed on moray eels and numerous fish species that live on the seafloor.

8. Yellow-bellied sea snake

The yellow-bellied sea snake, Hydrophis platurus, is one of the most widely distributed snakes in the world. Unlike other sea snakes, it is completely pelagic, found in all tropical ocean waters around the world except for the Atlantic Ocean. Hydrophis platurus is the most commonly seen sea snake species in the world. Measuring between 2.2 ft to 3 ft, they are large sea snakes from the subfamily Hydrophinae.

The yellow-bellied sea snake has a distinctive color pattern; a yellow underbelly and dark brown scales (hence the name, yellow-bellied), making it easily distinguished from other sea snake species. This incredibly venomous sea snake has a unique ability to swim backward, and they hunt by floating on the surface of the water to attract pelagic fish.