A video footage of Facebook account Thach Nguyen showing a group of 30 dolphins swimming off the Nha Trang coast on April 4 has gone viral online with 1.3 million shares.
Many Vietnamese netizens remarked that it was a "strange," "rare" and "surprising" phenomenon.
Vo Van Quang, an expert at the Nha Trang Oceanography Institute, said that the Nha Trang sea sometimes sees a few dolphins that have been "lost" to the shore. However, the sight of dozens of dolphins swimming in local waters "is quite rare."
Since tourist activities have been suspended in Nha Trang Bay in the wake of the coronavirus pandemic, the sea is quite quiet and dolphins can follow their prey freely in waters close to the shore, Huy said.
Locals also agreed that the suspension of tourism and the absence of tourist boats might have created favorable conditions for dolphins to gather in numbers closer to the shore.
Nha Trang Bay in the central province of Khanh Hoa is well known worldwide for its beaches and related attractions including scuba diving. It draws large crowds of foreign tourists, backpackers and more affluent travelers, as well as Vietnamese tourists.
Last week another group of dolphins appeared off Hon Cau Beach in Tuy Phong District in Binh Thuan Province, and it was filmed by a staff of the Hon Cau Marine Protected Area.
Binh Thuan is home to the resort town of Mui Ne, a popular vacation spot often referred to as "a seaside paradise". Over the last few years, it has added many water sports like windsurfing, surfing, jet-skiing, and kayaking.
Elsewhere in Vietnam in recent years, dolphins have appeared in groups in the waters off Hoi An Town in the central province of Quang Nam and Phu Quoc, Vietnam’s largest island in the Mekong Delta province of Kien Giang.
Whales and other cetaceans including dolphins are considered sacred by Vietnamese fishermen who believe that saving injured whales and dolphins and giving proper burials to those that die ashore are activities that will bless them with luck, good weather, bountiful catch and protection while at sea.