Devon Wildlife Trust Marine Awareness Office Coral Smith said humpbacks were now a “fairly common” sight and the whale in the video looked like a juvenile.
Smith warned all watercraft should maintain a safe and respectful distance away from marine mammals.
“Whales, dolphins and porpoises are legally protected and is therefore illegal to intentionally or recklessly disturb them,” she said.
“Anyone who observes harassment should call the police.
She added: “You can see in one video the humpback became briefly entangled in creel line.
“Unfortunately this is another all too common threat, particularly for humpbacks.”