Scientists have revealed that two species of deep-sea sharks, six-gill and prickly sharks, are positively buoyant — they have to work harder to swim downward than up, and they can glide uphill for minutes at a time without using their tails.
Scientists have revealed that two species of deep-sea sharks, six-gill and prickly sharks, are positively buoyant — they have to work harder to swim downward than up, and they can glide uphill for minutes at a time without using their tails.