A man, known only as Harry, was out with his family when he spotted the gull floating in the water while trapped in fishing tackle.
Despite a summer of reports that led to Prime Minister David Cameron calling for a “big conversation” on “killer” gulls he saved the bird.
Harry rescued the bird from Sovereign Harbour, in Eastbourne, East Sussex, on Thursday night so it could live to fly another day.
The bird was caught in fishing rigging and had 15 hooks tangled in its feathers leaving it unable to get out of the water.
East Sussex Wildlife Rescue and Ambulance Service treated the bird’s wounds and are planning to release it back into the wild.
Rescuer Jen Holloway said: “It could barely hold its head up when we arrived and it quickly became clear that our rescue nets couldn’t reach the bird and our boat was too far away to be of assistance quickly enough.
“Harry then did something truly amazing and swam out to the bird.”
Risking becoming entangled in the line and caught on hooks, the member of the public managed to swim the gull to shore where rescuers were then able to take over and save the gull.
Family pets, including two dogs and a tortoise have been killed by seagulls in recent weeks amid fears they are becoming more aggressive.