While this couple were out at sea, something suddenly rose up from the depths beneath them – and they would be faced with a sight that few divers ever see.

It was like a scene out of a blockbuster. A pair of Australian adventurers were out at sea filming sea turtles when they were joined by something entirely unexpected. Yes, unbeknownst to the duo, they would encounter a truly extraordinary sight, and it was a phenomenon that few professional divers – much less normal folk – ever experience.

When Brad Nicholls and Emmy-Rose Curtis got their hands on some new high-tech filming equipment, they decided to head out to sea to test out the gear. However, they had no idea what was in store for them that day.

The pair set out to go to South Stradbroke Island, nearly two miles off the Gold Coast Seaway, on a boat belonging to a friend. Next, they found the perfect spot in which to begin their swim, taking the underwater GoPro cameras with them. But they were soon joined by something far bigger than they had been anticipating.

First, though, the pair decided to dive straight in to see what they could find. They were expecting to spend their day taking snaps of peaceful sea turtles and colorful fish, and they had no idea what they were about to be faced with.

What’s more, with the trip arranged on the spur of the moment, Nicholls and Curtis hadn’t come fully prepared. So, without goggles or diving gear, the couple were about to find themselves feeling very exposed when they came up against the unexpected.

It was at this moment that something rose up from the depths beneath them – and what an entrance. You see, it was a creature measuring some 40 feet long and weighing nearly 90,000 pounds. Perhaps surprisingly, however, the pair were unafraid.

The adventurers had in fact been joined by a mother humpback whale and her calf. It was a truly unique experience. And as Nicholls told Yahoo7 News, “Having it that close, I wasn’t going to let that opportunity pass by, having them all around us… You’re never going to do that again.”

That said, the creatures could have posed a significant threat to the divers. Whales are massive animals, after all, and they’re capable of effortlessly killing humans. Yet what followed was both astonishing and beautiful.

Fortunately, it’s worth remembering, Nicholls and Curtis are not amateurs. They actually have years of experience when it comes to watching and studying whales in the wild. The pair consequently read the creatures’ signals and knew how to deal with the situation. What’s more, their encounter lasted for over an hour – during which time they filmed some truly amazing footage with their new GoPros.

“Their movements were so gentle and so slow, almost like they were like, ‘Oh, I don’t want to hurt my new friends,’” Curtis told ABC7NY. “In ten years, I have never seen this type of behavior for whales with a boat, let alone with us in the water.”

“We kept getting out of the water, and they would be coming up to the boat and spy hopping as if to say, ‘Where’d you go? What are you doing? Come back and play,’” Curtis told Yahoo7 News.

These gentle giants were obviously intrigued by their new guests, and they displayed no signs of aggression. This didn’t make the adventurers’ run-in with the giants any less dangerous, mind you. And considering the threat, the pair knew that they had been lucky.

Indeed, Curtis actually had doubts about whether or not she should post the video online. After all, she reasoned, it might well inspire others to venture out to the same area to try and replicate the experience. However, in the end the diver made up her mind and shared the extraordinary footage that the pair had captured. The film was simply too impressive to keep a secret.

Now, then, the video has been enjoyed by more than 350,000 viewers on YouTube. The astonishing images even show the whales waving their fins as well as playing with their new friends. And it all goes to show just how curious and intelligent these massive creatures are.

Since the couple’s experience, a number of tour operators have consequently looked into offering whale swimming excursions in the area. Yet while trips of this type are available in Western Australia and on the Sunshine Coast, strict regulations make them less feasible in the vicinity.

Scott Wilson is one whale watching tour operator who has been testing the waters. He has found, however, that the rules make whale swims like this generally too problematic to be viable.

The New South Wales Environment and Heritage office refuses to license swimming with whales outside of marine parks. It also states that swimmers are forbidden from getting into the water within 320 feet of one of the creatures. And if a whale does come within 100 feet of a person, then they must not approach, touch or alarm it.

Nevertheless, Wilson has managed to run two test dives with a small number of swimmers; and in an interview with the Gold Coast Bulletin, he explained his approach. “The whales are curious,” the tour operator said. “They come over to you. They choose if they want to swim with us. We don’t determine that.”

The key point, however, is that visitors do not drive the whales away or pollute the waters. But in the meantime, individuals like Wilson will pursue compromises that allow tourists to get a closer look at the natural world.

Meanwhile, what there’s little doubt of is that Nicholls and Curtis had a truly spectacular experience. And – at least for the time being – it is likely to remain a rare one.