A breach of the warning could result in further prosecution under the Anti-social Behaviour, Crime and Policing Act.
Police sergeant Martin Easter said: “We’re lucky to have a vast amount of wildlife across the bays in Cornwall. Whilst sightings of these animals is exciting, it’s important we respect their space.
“In this case, the individual had no regard for the dolphins or how his deliberate behaviour could cause a disturbance, even hailing for more people to come over and join him in doing so.”
Sgt Easter added: “Our ask is that people enjoy our waters, but to make sure they do so safely and responsibly.”
People should try to stay at least 100 metres, or 330 feet, away from marine mammals while in the ocean.
If this is not possible, they should leave as much space as they can, police said.