I mentioned that while swimming at Miami Beach, a manatee swam by, and it spun around on its long axis a few times. It wasn't feeding but once it breathed while belly-up (not typical for manatees). Spinning may have been a way for ancestral sea cows to pull sea grasses and seaweeds rooted in benthic soils, later lost due to improved mouth/teeth/lip evolution. This article describes how blue whales spin 180 degrees, then continue to 360 degrees, while feeding on krill.
BBC Nature - Largest whale's acrobatic ambush
Tubular turns
"As the blue whale approaches the krill patch, the whale uses its flippers and flukes to spin 180 degrees so that the body and jaws are just beneath the krill patch," explained Dr Goldbogen.
"At about 180 degrees, the mouth just begins to open so that the blue whale can engulf the krill patch from below.
As the blue whale engulfs the prey-laden water, it continues to roll in the same direction and completes a full 360 roll and becomes horizontal again ready to target and attack the next krill patch."
BBC Nature - Largest whale's acrobatic ambush
Tubular turns
"As the blue whale approaches the krill patch, the whale uses its flippers and flukes to spin 180 degrees so that the body and jaws are just beneath the krill patch," explained Dr Goldbogen.
"At about 180 degrees, the mouth just begins to open so that the blue whale can engulf the krill patch from below.
As the blue whale engulfs the prey-laden water, it continues to roll in the same direction and completes a full 360 roll and becomes horizontal again ready to target and attack the next krill patch."