"We were shocked about the incident as it creates a bad image for Namibia," Kenneth Nependa, vice-chairperson of the Federation of Namibian Tourism Associations, told the Namibian Sun.
In the video clip, the trio stripped their clothes to take photos after hiking up the sandbank, which is more than 300 meters tall, New York Post reported.
Authorities have not yet publicly identified the tourists but slammed them for "disrespecting the country's laws and traditions."
The Namibian government is considering banning the naked visitors from entering any of the nation's national parks in the future.
Big Daddy is one of the three largest dunes in Namibia's Namib-Naukluft National Park and is a popular destination among tourists.
Popular tourist hotspots have reported incidents of nude tourists disrespecting their culture and traditions.
In October last year, a foreign man to Bali was filmed meditating naked at a Hindu shrine, prompting officials to deport him.
That incident came after another tourist to Bali was detained by police after posing naked by a sacred tree in April 2023.