Whale sharks, which can grow to around 10 metres in length, are slow-moving filter-feeders and pose no threat to humans, but Gulliver sparked alarm in Nukunonu atoll among locals who assumed he was a man-eating shark.
In May this year, a team of Australian researchers arrived in Nukunonu, after being summoned by a local teacher who suspected the animal was a whale shark and hoped to put fears to rest, said Brad Norman, one of the researchers.
By that point, it had been around six months since people in Nukunonu had been allowed to go into the lagoon.
"We had a massive shark but we didn't know it was a whale shark until [the researchers] came," said Elena Pisilio, who writes for a local newspaper in Nukunonu.
"So the parents started telling their kids they weren't allowed to go to the sea because everyone thought it was a hammershark or those other scary sharks," she said.
From above, Nukunonu looks like a slightly squashed pentagon, with the thin strip of land running along the edge of the atoll sheltering a peaceful turquoise lagoon from the rough waves which relentlessly hammer the sea wall on the other side.
There would be few places safer for a young whale shark to grow up in.
But for a while, Gulliver appeared to be in serious danger.
A member of the Nukunonu Taupulega, or village council, had suggested killing the whale shark, or trying to remove it from the lagoon, said Mr Norman.
Worried for the whale shark's safety and wanting to study what is believed to be the first documented case where the animal has been trapped in a lagoon for a lengthy period of time - at least two years, locals estimate - the researchers embarked on a mission to find it.
Over the course of seven or eight days, they were joined by an armada of nearly 30 dinghies manned by at least 50 Nukunonu locals, assisted by drone fly-overs, said Mr Norman.
Eventually, when they had found Gulliver, locals joined the researchers in jumping into the water near him - making sure not to crowd the whale shark.
Nukunonu locals adopted the name Gulliver from a namesake stuffed whale shark toy Mr Norman takes with him wherever he goes to research the animals.