When students from the educational program Master Mint went on a field cruise in waters off of Portugal's Azores Islands a few years ago, they had no idea that they were about to witness an historic first.

"A small inflatable boat stopped in blue calm deep waters near the coast of the Azores," Natacha Aguilar de Soto of the University of La Laguna and the University of St. Andrews told Seeker. "Suddenly, four beaked whales appear from nowhere and swim slowly around the boat, with deep blows, allowing the teacher to film them from the boat with a small underwater camera."

She continued, "Nobody on board recognized which species of beaked whales they were watching at just 5 m (16.4 feet) from the boat, and nobody knew that they were filming an historical first: underwater video of True's beaked whales!"

Aguilar de Soto and her team recently identified the secretive whales in the unprecedented footage as part of a new study published in the journal PeerJ. The study compiled sightings in the Azores and Canary Islands, as well as stranding data, in order to better document True's beaked whales.

Little is known about the cetaceans because the whales — which are named for Frederick W. True, an American biologist who first described the species in 1912 — spend about 92 percent of their time underwater. They are believed to dive nearly two miles below the surface, and to remain at such depths for up to two hours.

RELATED: Video Slideshow: Wondrous Whales from Drone's Eye View

The video reveals that True's beaked whales can travel in small groups. In this case, the group consisted of three to four adult females or juveniles. The whales forage using suction or grabbing, so only adult males have teeth. Researchers suspect that males use the teeth in fights and assertive displays, similar to how male deer brandish their large horns.

By studying the images collected for the study, Aguilar de Soto and her team identified the first photos of a True's beaked whale calf. The scientists also discovered a new coloration pattern in the species.

Photo: First known image of a True's beaked whale calf, seen with an adult. Credit: Ida Eriksson

Senior author Emma Carroll of the University of St. Andrews told Seeker that the "new color pattern is a white mask. Typically, in the North Atlantic, True's have a greyish pattern."

If the color is found to be common in True's beaked whales, then "it means that it might be more difficult to tell the different beaked whale species apart in the wild than previously thought," Carroll said.

RELATED: Beached Beaked Whale Likely Killed by Boat

She explained that similar white colorations are sometimes found in a species called Cuvier's beaked whale.

The study, which represents one of the largest collections of True's beaked whale sightings at sea, further determined that these marine mammals favor waters off the Azores and coastal regions off the Canary Islands. Both sets of islands are oceanic volcanic archipelagos that rose from the seafloor of the Atlantic. As a result, the water around these islands is very deep, and is therefore suitable for the deep-foraging whales.

Photos: Male True's beaked whale breaching. Credit: Dylan Walker

The researchers hope that by better documenting True's beaked whales and their habitats, they can monitor the status of the whales' populations and improve their conservation.

Prior to the new study, True's beaked whales were mostly known from mass strandings that occurred following naval exercises that involved intense sonar signals to detect submarines, or from whales washing up dead on beaches with their stomachs containing large amounts of plastic and other garbage.

"The oceans are immense and full of life," Aguilar de Soto remarked. "They still hold mysteries like the True's beaked whale, waiting to be discovered. What we do on land affects what happens in the deep waters where beaked whales live."

Top Photo: One of the first known underwater images of True's beaked whales. Credit: Roland Edler