Three people were pulled from the water when their speedboat began to sink in the Irish Sea, the RNLI said.
Another leisure boat in the area responded to its Mayday alert and rescued the three adults about a mile off Bray Harbour in Co Wicklow.
They were said to be cold when brought ashore, but did not need medical attention.
The incident happened shortly after midday when the 15 foot speed boat filled it water from a large wave that crashed in to it.
The RNLI lifeboat from Dun Laoghaire and the Greystones Coast Guard found the boat, which was almost fully submersed, and towed it ashore.
Conditions were said to be changeable at the time with choppy waves, but winds gusted to storm force towards the end of the rescue operation.