The coastguards of Guernsey and Jersey are asking for watercrafts to be stored out of reach of high tide after two false alarms led to searches.
Abandoned kayaks were found in the water after coming loose from where they were kept on the coast.
A craft was found adrift near Jersey on Sunday which had no identification, making the owners difficult to trace, prompting a coastguard search.
A similar incident happened when a kayak was found off Guernsey.
"We recommend that owners do not store watercraft in coastal locations, especially when not in regular use, as this increases the risk of them becoming dislodged or breaking free and being carried away by the tides," said Guernsey's harbourmaster, David Barker.
The crafts the coastguards are concerned about include kayaks, paddle boards and dinghies.
They are encouraging people to use a voluntary watercraft registration scheme.
"In return for providing us with details of their watercraft and their own contact, owners receive a unique identity number in the form of a weatherproof vinyl sticker or robust tag, which is then affixed to the craft," said Jersey's harbourmaster Bill Sadler.