Charoen Chanapo was leading a boat of tourists through the Andaman Sea in Thailand when he spotted a large creature in the water.
It was a humpback whale, according to an Aug. 23 Facebook post from Phuket Info Center.
The boat was heading from Phuket to the Phi Phi Islands, the center said.
The enormous creature was moving from southeast to southwest, the center said. It lifted its tail and then disappeared back into the water.
Humpback whales are a rare sight in Thai waters, according to the post. The sighting is only the second time a humpback has been seen in the area.
A video of the encounter shared on Instagram by Seahorse Marine shows the huge creature diving through the water.
Humpback whales are known in all of the world’s oceans, according to the National Oceanic and Atmospheric Administration. In the Pacific, they are known to breed near Japan and the Philippines and feed off the Russian coast.
Phuket is an island in southwest Thailand, about 430 miles southwest of Bangkok. The Phi Phi islands are in the Andaman Sea east of Phuket.
Google Translate and Baidu Translate were used to translate a Facebook post from Phuket Info Center.