What would you do if an animal the size of a submarine wanted to give you the once-over?

An inflatable boat full of tourists found out recently in Hawaii, when two humpback whales circled their boat for at least 10 minutes, according to a report by Hawaii News Now. The female humpback whale bumped up against the boat as if she were scratching her back, a crew member for the tour company, Captain Zodiac Rafting Expeditions, told the site.

As the whales approached the boat, shouts of excitement ring out in a video posted online by the tour company.

Humpback whales seem the most curious of all the large whale species, said Jooke Robbins, a senior scientist at the Provincetown Center for Coastal Studies in Massachusetts and director of the center's Humpback Whale Studies Program.

"It's not just boat-related. A colleague of mine saw this curious approach at an iceberg," Robbins told OurAmazingPlanet.

The way humpback whales approach boats, icebergs, clumps of seaweed or other large objects in the water is almost a stereotypical behavior, Robbins explained.

"They will circle around it, sometimes they will go belly up underneath it, and they are very careful in the approach," she said. "Often, their eyes are closed while they are doing it."

Sperm whale seeks robot

Humpbacks are the not the only curious whales, though. Deep-diving sperm whales, notorious for nipping fish off longline fishing lines in Alaska, are also starting to pop up on YouTube videos. In the underwater video seen here, a massive sperm whale checks out a remotely operated robot.

Because sperm whales aren't at the surface as much as humpback whales, scientists know less about their behavior, Robbins said. She added, "There is certainly a type of apparent curiosity, such as approaching boats and other things, that has been seen in different forms in many of the large whales." [Images: Sharks & Whales from Above]

Scientists still don't understand what the inquisitive behavior represents to whales, Robbins said. For example, she is not convinced the humpback whale seen in the tourist video was scratching its back on the boat. "It takes them a while to go over and touch a novel thing," she said. "They are very, very careful about touching."

Keep your distance

Robbins did praise the tour company for their interaction with the whales. A "code of conduct" published by the National Oceanic and Atmospheric Administration asks people to avoid approaching whales too closely. The guides let the whales come to them, which is permitted, and turned off their engines.

"It's important to remember that something like this is a precious thing," Robbins said. "It's important to keep a respectful distance. Many of these species are still considered endangered, and where we like to look at them is in critical breeding habitat."

Whale watching seasons started Aug. 30, 2012, in Hawaii, which may have been the earliest the mammals have ever been seen in the area, according to a statement from NOAA. About 10,000-12,000 humpback whales visit Hawaiian waters every year to mate, give birth and nurse their calves in the warm waters, where they are protected.

Reach Becky Oskin at [email protected]. Follow her on Twitter @beckyoskin. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.