Horrified onlookers saw a teenage boy calling for help after getting stuck in mud along a riverbank.
The boy was walking along the River Adur in Shoreham when the incident happened shortly before midday on Sunday.
He sank slightly and struggled to free himself.
Members of the public rushed to his aid along with various emergency services personnel.
The coastguard said the teenager had eventually managed to free himself and did not need any medical assistance after the incident.
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A spokesman for HM Coastguard said: "Shoreham RNLI lifeboat, Shoreham Coastguard Rescue Team and West Sussex Fire and Rescue were sent to a report of a person stuck in mud on the banks of the River Adur in Shoreham.
"The alarm was raised at just before midday on 14 July. The individual self-recovered."
A spokesman for Shoreham RNLI said: "Our inshore lifeboat was tasked to a report of a teenage boy stuck in the mud in the River Adur by Shoreham Airport on Sunday morning.
"Once on scene it was established that the casualty had been assisted by a member of the public and other emergency services. The call was good intent."
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