The Coast Guard is urging people to stay away from coastal areas where there is sea fog, warning that they can quickly become isolated by it.
The alert was issued following two incidents in Dublin on Tuesday evening.
Three teenage girls were rescued after they became lost in fog on Sandymount Strand.
Elsewhere, a woman was taken to hospital after she fell on rocks at Bullock Harbour near Dalkey.
Sea fog is forecast along areas of the east coast.