The Coast Guard is urging people to only take part in organised sea swims this Christmas.
Hundreds are expected to take part in traditional Christmas Day swims in places including Cork, Waterford, Galway and Dublin.
Fergal Somerville from the Easter Bay Swim Team in Dublin is taking part in an charity swim at Portmarnock beach.
He has this advice for those preparing to take to the water this morning: "A couple of very very important points, you should spend a minumum amount of time in the water.
"Most of the people who go out on these swims haven't been out as regular swimmers all year round so they get in they get wet, they get out, they get dry all in a matter of minutes."