Waves of up to 14 metres in height are being predicted for the west coast this weekend.
They would be the highest experienced for a number of years.
The Marine Institute and Met Éireann have issued a warning to all ships, fishing vessels and anyone close to the shoreline to take great care, particularly tomorrow afternoon.
Computer-generated wave forecasts, using information picked up on the Marine Weather Buoy Network, show that waves with a significant height of up to 14m, about 45 feet, could occur in the seas to the west of Ireland.
Previously the biggest waves recorded by the Marine Institute's data buoys were at the M1 Buoy to the west of Galway Bay on 17 January 2005, waves of 13.4m or about 40 feet.
The Institute and Met Éireann say that similar conditions could occur this weekend if weather systems develop as predicted and create conditions potentially hazardous to all marine users.
When a broad area of very low pressure sits in the Atlantic north of Ireland, as is expected to happen today and tomorrow, waves are able to build over a considerable distance.