The animal was spotted by a group of tourists at midday.
A local tourist guide, Nhat Phong, said that many visitors in his group were excited to see the whale shark. “They shouted loudly but the animal seemed not scared and swam closer to us," Phong said.
Phong recorded the swimming animal and posted it on his Facebook account, which received thousands of likes and comments.
Speaking to Dantri/Dtinews, a representative from the Nha Trang Institute of Oceanography, Vo Van Quang, said that the whale shark, with the scientific name Rhincodon typus, was the largest species in the Chondrichthyes group.
"It is estimated that whale sharks are between 9-11 metres in length and weigh between 10-15 tonnes," he said. "They have a life expectancy of between 80-130 years."
Another shark whale was also spotted off the coast of Binh Dinh in 2010.
Earlier this year, another tourist guide also saw two whales swimming off the coast in Phu Cat District. Local people, especially fishermen, believe it is lucky to see whales.