The RNLI Brighton lifeboat was launched after two kitesurfers were reported to be in difficulty in the sea off Hove.
A short while later the lifeboat crew spotted their kitesurfing kit was found washed up on the beach but with no sign of the kitesurfers themselves.
At the same time a coastguard unit tracked down someone ashore who matched the description of one of the kitesurfers.
Brighton RNLI operations manager Roger Cohen said: “Even though the call turned out to be a false alarm, we would like to commend the member of the public who did the right thing by calling 999 to report what they saw.
“They thought someone had gotten into trouble and had good intent calling the authorities.
“We would rather launch to investigate what was seen and put everyone’s mind at ease.
“This call also highlights the importance for watersports equipment to identify the name and contact details of the owner.”
The sea search started last Wednesday morning (27 October) after a concerned member of the public reported seeing two kitesurfers who looked to be in difficulty in the sea off Hove.
The volunteer crew was asked to launch the in-shore lifeboat Random Harvest by the Coastguard just after 9am.
The crew searched between Hove Lagoon and Rockwater – and the callout was later updated when the kit was found washed up on the beach with no sign of the owners.
Once the shore-based coastguard unit identified one of the kitesurfers and established that the pair were safe, Solent Coastguard stood down the lifeboat crew.
The lifeboat was back at Brighton Marina and ready for service again at 10.10am – and the call was classified as a false alarm with good intent.
Weather conditions at the time were good with a light south-westerly breeze, calm sea conditions and good visibility.
The coastguard urged those taking part in watersports to mark their equipment and other items with their name and contact details in case it is lost, stolen or abandoned. It can also help when checking whether someone is safe.
The coastguard added: “This really helps us to save a lot of time and could provide us with extra information we need to help you if we believe you’re in difficulty at sea.”
Suitable labels can be ordered free from the Maritime and Coastguard Agency website.
At the very least, some users simply write their mobile number on their equipment with a permanent marker.
If someone appears to be in trouble in the sea, call 999 or 112 and ask for the coastguard.