Video shows humpback whale circling around Australian tourist boat for nearly an hour

A group of whale-watching tourists got more than they bargained for in a recent trip off Australia's coast.

A massive whale circled a boat near Sydney for nearly an hour Aug. 16, leaving the 21 passengers stuck in place until it left, according to Blake Horton, who owns tour boat agency Ocean Extreme.

Video captured the humpback keeping the vessel hostage, offering watchers an unforgettable up close view. The screams of excited tourists can heard as the whale pops its head out of the water.

"This does occur from time to time. When they get very curious about the boat you have to wait until they move away before you can put the boat into gear again," Horton said in a statement to USA TODAY Thursday.

Due to local regulations , the boats are required to turn off their engines before continuing its passage if an adult whale is less than 100 meters or 328 feet away, according to Yahoo News.

Watch video of whale holding Sydney boats 'hostage'

What is whale mugging?

Whale mugging is a term marine biologists use when a whale enters close proximity of a boat, according to Whale Watching website Ocean Odyssey.

"Sometimes during these 'muggings' they engage in another form of behaviour called 'spy hopping,' which is when a whale slowly lifts its head out of the water," the group said in a post.

The Ocean Extreme boat's captain Cassie Murray called the Aug. 16 moment very special as the whale "was just watching us watch it, basically," Yahoo News reported.

"The behavior we experienced, it’s called a mugging because, essentially, the boats are being held hostage by the whales, we can’t move," Murray told the outlet.

This article originally appeared on USA TODAY: Video shows humpback whale circling around Australian tourist boat for nearly an hour