Lifeboat and coastguard teams were called out amid reports of one person in the water near a small dinghy.
A search was carried out by the Beaumaris inshore lifeboat and coastguards from Penmon following the callout at around 4.10pm on Wednesday.
It was claimed another person was on board the dinghy.
But the search was stood down after 45 minutes after both emergency crews failed to locate anything.
A spokesperson for Beaumaris RNLI said: "This was a false alarm with good intent, and it is always better for us to be deployed than rather than make an assumption."
"As always, our collaboration with the coastguard team ensured a swift response to the this incident."
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