A British backpacker has been killed by a sea snake while working on a fishing trawler off the Northern Territory coast.

The 23-year-old was bitten by the reptile around midday on Thursday, while pulling up a net off Groote Eylandt, 650 kilometres east of Darwin.

According to police, the boat was five hours from land when the incident took place.

Emergency medical service Care Flight dispatched a helicopter to the boat, along with other ships in the area, as part of a multi-agency response.

But St John Ambulance operations manager Craig Garraway said the man couldn't be saved and he was pronounced dead once the trawler reached the town of Borroloola.

"A trawler off Groote Eylandt had reported that one of their male crewmen had been bitten by a sea snake," Garraway said.

"(Emergency responders) went out to the trawler but unfortunately by the time they got out there he had passed away.

"The Groote Eylandt health clinic and police responded to the trawler but unfortunately the male passed away at some point yesterday afternoon."

The British High Commission has been informed of the man's death. NT WorkSafe said in a statement it had started an investigation into the incident.

Charles Darwin University honorary fellow Dr Michael Guinea previously said sea snakes are "equally poisonous if not more poisonous as things such as our tiger snakes and western brown (snakes)".

According to the Marine Education Society of Australia no deaths have previously been recorded from sea snake bites in Australian waters. But there have been some close calls.

Earlier this year, Darwin fisherman Peter Davis nearly had his finger amputated after being bitten by a sea snake that was snagged on his line.

"We were just sitting at the mouth of Sampan having a fish, throwing some vibes around, and I happened to hook a sea snake on my vibe and while I was trying to find the scissors to cut it off it rolled up the line," he told the NT News.

"I felt it hit my hand and spun around and dropped the rod and cut it off... it must have just hit me with its teeth."

It wasn't until a couple of days later that Davis realised, that while he hadn't been envenomated, the snake's front teeth had left him with a nasty infection, the NT News reported.

The 23-year-old man's death marks the second in which a British man has recently died on an Australian fishing boat.

In 2013, 20-year-old Ryan Donoghue was electrocuted on a prawn trawler in the Gulf of Carpentaria. NT Coroner Greg Cavanagh found his death was needless.

"It would have been prevented if there was even a modicum of compliance with the law," Cavanagh said.