Most sharks are classified as negatively or neutrally buoyant. But a new study claims that two different species of deep-sea sharks have the ability to remain positively buoyant, which means they will not sink if they stop moving in the water.

Based on the study conducted by a team of scientists from the University of Hawaii-Manoa (UHM) and University of Tokyo, two species of deep-sea sharks, the prickly sharks (Echinorhinus cookei) and bluntnose sixgill sharks, (Hexanchus griseus) tend to float more than their shark relatives, Phys.org reported.

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UHM's Hawaii Institute of Marine Biology assistant researcher and study co-author Carl Meyer said that the latest findings came as a total surprise. He also added that he and his colleagues didn't expect that when they conducted two sets of experiments, it confirmed their initial observation that those deep-sea shark species showed evidence of positive buoyancy, The Weekly Observer has learned.

In order to determine the buoyancy status of the two species of deep-sea sharks in their natural habitat, The Standard Daily revealed that the scientists used accelerometer-magnetometer data loggers to document their swimming performance, which includes swim speed, tail beat frequency, heading and body orientation.

The compiled data from the data logger would provide the researchers with comprehensive insight about the shark's buoyancy, which is either negatively or neutrally buoyant or the opposite.

A majority of the shark species are considered negatively or neutrally buoyant. According to State Column, the bodies of the sharks are generally less dense than other fish and marine animals. Mostly, their skeletons are made completely out of cartilage.

So as to compensate the differences in density, most sharks generate buoyant force with a large, oil-filled liver, which helps the sharks with buoyancy. However, most will still sink if they stop moving through the water. And in order to stay above the bottom of the ocean, most sharks can never stop moving.

As per the latest finding, the prickly sharks and bluntnose sixgill sharks exhibit positive buoyancy, which means that the sharks exert additional effort swimming down and easily glide upwards without using their tails. However, cold water causes shark muscles to become sluggish.

The ability of being positively buoyant may be an advantage for the prickly sharks and sixgill sharks to hunt in deep habitats with much colder temperature since they spend the majority of the day at great depths.

Deep-sea sharks only travel into the shallows when the water has cooled during the night. The observed positive buoyancy may give these shark species an evolutionary advantage in the cool, deep-sea environment where access to food is limited. Researchers suggest that the buoyant force could either help the sharks sneak up on their prey from below or help them conserve energy as they make their way back to shallow waters each night.

Meyer and his colleagues wrote the findings of their study in the journal PLOS One, which was published on June 10, Tech Times noted.

Tagsshark, Buoyancy, Study, Science, Deep Sea Creatures, marine life