Marine rescue services have been called out to 14 incidents involving jet-skis and 82 involving powerboats so far this year, according to the Irish Marine Emergency Services.
Most were said to be concentrated on the east and south-east coast on a line from Youghal, Co Cork, to Carlingford, Co Louth.
It is understood there had been only one previous death involving a jet-ski in the State before this week, when a Belfast man died from injuries sustained in an accident at Mullaghmore, Co Sligo, in July 1999.
Mr Glen O'Hare (19), was riding the watercraft, which in turn was towing a youth on water-skis, when it collided with another pleasure craft in the harbour.