Lifeboat and helicopter crews were scrambled after reports of a “man overboard”.

An RNLI Sheerness lifeboat was launched after a dinghy had been seen drifting off the Isle of Grain.

The crew of the lifeboat, Judith Copping Joyce, had taken to the water at 9am on Tuesday, April 9 and found the dinghy within 10 minutes.

It had run aground in the mud at West Shore and there were no signs of a person being involved so the crew assumed the craft had come adrift from a mooring.

The lifeboat was stood down but a signal was received from a “man overboard” device.

The alarm was reported to the coastguard at Dover and the Medway Vessel Traffic Services.

The coastguard requested a search of the River Medway upstream to Darnett Ness.

It launched a coastguard helicopter that searched the Sea Reach area.

Nothing out of the ordinary was found by either the lifeboat or the helicopter so both were stood down at 10.20am.

It later emerged that a marine services employee working out of Sheerness Docks had accidentally set off the alarm.