A swimmer was hospitalised after separating from their group at Dalkey Island on Saturday.
Luckily, they were wearing a bright coloured swim cap and had a safety float which made it easier for emergency services to identify them.
They were located soon after the search began and were taken ashore to Coliemore Harbor and were then transported to hospital.
The Dun Laoghaire Coast Guard unit praised the swimmer's group for raising the alarm quickly.
They said on social media: "The swift actions taken by the group to alert the Coast Guard to the overdue swimmer assisted in a prompt response from the emergency services and to locate them as swiftly as possible."
In a separate incident on Sunday, the Coast Guard received a call about a "nuisance jetski" at Killiney beach.
When emergency services reached the scene, the jetski had left the area.
They reminded the public not to drive near yellow markers on the water.
They said: "The yellow safety makers near bathing areas are for the safety of swimmers and you must keep away from these locations and not use the markers to drive around."
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