True’ sea snakes and sea kraits are some of the most venomous animals in the world. There are more than sixty species of ‘true’ sea snakes. Most of these species spend their entire lives in the ocean; however, they still breathe air.
What's the difference between sea snakes and sea kraits?
Their lungs are adapted to their marine lifestyle. Sea snakes have one enlarged lung that runs along the length of their whole body, enabling them to stay underwater for a long time. They also have nostrils on top of their snouts so that they do not have to poke their heads out of water to breathe.
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Sea kraits, on the other hand, are only semi-aquatic.
There are eight species of sea krait, and they lay eggs on land, unlike sea snakes which give birth to live young underwater. Also unlike their sea snake cousins, sea kraits do not have nostrils on top of their snouts, but – like terrestrial snakes – have them on the side of their snouts, instead.
And while sea snakes can stay underwater for multiple hours without needing to come to the surface to breathe, sea kraits tend to stay submerged for less than an hour at a time.
Despite their differences, almost all species of sea snakes and sea kraits are venomous, and their venom is highly potent. It is so potent because when these creatures bite their prey, their venom becomes diluted by seawater. The venom therefore needs to be very potent in order to balance out the effect of this dilution.
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Thankfully, both sea snakes and sea kraits are generally timid creatures, and do not often bite people.
But, not all of them are shy…
Below is a list of six of the deadliest sea snakes and sea kraits in the world.
Deadliest sea snakes
Olive Sea Snake
(Aipysurus laevis)
Olive Sea Snakes, which have olive-green heads and can grow over six feet long, are found in the coral reefs of the western Pacific and eastern Indian ocean. They hunt at night, weaving through reefs in search for their prey – usually small fish and crustaceans.
Their venom, which they use to incapacitate prey before eating it, is so potent that one bite can kill a person. But they rarely bite – they are better known for their curious, playful inspection of divers than for any aggression.
Interestingly, this species has ‘photoreceptors’ in its tail. This means that their tails can detect light, which might help the snakes to stay super-duper hidden, ensuring not even their tails can be seen.
This peculiar light-detection ability is shared with some of the Olive Sea Snake’s closest relatives, but it is not shared with all sea snakes.
Yellow-lipped Sea Krait
(Laticauda colubrina)
A graceful and deadly sea krait found in tropical Indo-Pacific waters, the Yellow-lipped Sea Krait is a black-and blue striped beauty with – you guessed it – bright yellow lips.
Most often spotted moving through reefs on the hunt for its prey, this is a docile species who will usually swim away from divers. However, because they are sea kraits and therefore spend some of their time on land, bites have been known to happen when they have been stepped on or even picked up by beachgoers.
The Yellow-lipped Sea Krait’s venom is neurotoxic. While their bite might not hurt too much, the victim will soon begin to have severe neurological symptoms including fits, paralysis, cardiac failure and – sometimes – death.
Yellow-bellied Sea Snake
(Hydrophis platurus)
Found in all tropical waters except from in the Atlantic, this species – with a striking bright yellow underside – is the only sea snake to have made it to Hawaii, and has even been found in some cooler regions like California.
Their venom is incredibly potent, but like most sea snakes they are not aggressive and avoid humans where possible.
When a person is bitten by a Yellow-bellied Sea Snake, they may – at first – have mild symptoms such as localised pain. But symptoms can develop quickly, and this species’ venom can cause paralysis, respiratory failure, and death.
Surprisingly, sea snakes need to drink fresh water in order to survive – they cannot survive by drinking seawater. The Yellow-bellied Sea Snake has been observed getting its fresh water by drinking rain that settles on the surface of the sea.
This species can last a long time without proper hydration, though – it can last up to seven months without a drink of fresh water!
Stokes's Sea Snake
(Hydrophis stokesii)
This species is large – growing up to five feet in length – and is one of the heaviest of all sea snakes.
As with the other species of sea snakes and sea kraits, its venom is neurotoxic and could potentially lead to cardiac arrest and death if it bit a human.
However – despite the fact that it has the longest fangs of all marine snakes and could easily puncture a wetsuit – there haven’t been any recorded fatalities caused by this species.
Dubois' Sea Snake
(Aipysurus duboisii)
The Dubois’ Sea Snake lives in coral reefs off the coast of Papua New Guinea, New Caledonia and Australia. It eats moray eels and is rather shy of humans.
This sea snake has got the deadliest venom of all sea snake species, and is one of the top three most venomous snakes in the world – behind the Inland Taipan and the Eastern Brown Snake (both terrestrial snakes).
However, despite its incredibly potent venom, the Dubois’ Sea Snake does not cause many human fatalities. It is a docile and timid creature, unlike the next snake on the list…
Beaked Sea Snake
(Hydrophis schistosus)
Another resident of Indo-Pacific waters, the Beaked Sea Snake does not have the most potent venom – that’s the Dubois’ Sea Snake – but it is has caused the most human fatalities of all sea snakes and sea kraits.
So what makes them the deadliest sea snake?
Unlike almost all other sea snakes and sea kraits, the Beaked Sea Snake is known for its aggressive nature. Indeed, scientists who study them have called them “cantankerous and savage”.
Up to 90% of human deaths from sea snakes are because of this species. Most of these fatalities are in fishermen who come into contact with the snakes when hauling in their nets. Waders and swimmers are also at risk, though.
So, while the Beaked Sea Snake may not have the deadliest venom, it is by far the deadliest sea snake when it comes to human fatalities – in fact it is one of the deadliest animals in the sea.
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