Fishermen in the Gulf of Thailand filmed a rare encounter with pink dolphins, which scientists say are becoming bolder in the absence of tourists during the coronavirus pandemic.

The footage shows three pink dolphins swimming close to a fishing boat in calm waters off Koh Pha Ngan, an island in southeastern Thailand.

"I was so impressed because I never imagined I would get to see pink dolphins," said Chaiyot Saedan, the fisherman who provided the video to Reuters.

Thailand's pink dolphins are a subspecies of the Indo-Pacific humpback dolphin and are listed as a vulnerable species by the International Union For Conservation of Nature.

There are around 150 of these pink dolphins living around the Gulf of Thailand, according to Kongkiat Kittiwatanawong, the director of the Phuket Marine Biological Center.

"Due to less traffic with the coronavirus lockdown, dolphins now have a more comfortable habitat, and that's why they tend to show up more," Kongkiat told Reuters over the phone.

Tourism in Thailand has plunged more than 76% in March from a year earlier, as the country was hit by the coronavirus outbreak.