A group of fishermen spotted and filmed the whales 22 kilometers away from the coastal area of Jiwani, according to the Pakistan chapter of the World Wide Fund (WWF).
It said the fishermen, including some trained and quipped by WWF to observe marine life, spotted the spouts of two whales on Sunday and chased them out of curiosity for about one-and-a-half hours until they took a deep dive and disappeared into the sea.
"Eventually, the whales turned out to be a pair of sperm whales which had never been reported live from Pakistani waters," said WWF's Muhammad Moazzam Khan.
He said that skeleton of a sperm whale was reported in 2005 near the southern port city of Karachi and a few bones of another specimen were also found in Jiwani.
"I am very excited about seeing them in Pakistani waters. Until now regional experts were reading about it in books and seeing sperm whales in TV documentaries," an evidently excited Khan told VOA.
The sperm whale is the largest of the toothed whales and has the largest brain of any creature on earth. They are easily recognized by their massive heads and prominent rounded foreheads, experts say.
The giant mammal mainly eats large squids and can dive as deep as 1,000 meters, (3,280 feet) in search of food, about one ton a day, and they can hold their breath for up to 90 minutes on such dives.
The size of a sperm whale is up to 12 meters in length and can weigh up to 58,970 kilograms