Sean McNair, 17, was last seen in the water at Rathmullan Pier after midnight yesterday.
He is believed to have been at a birthday celebration and was with a group of teenagers who went swimming.
His family and friends are maintaining a sad vigil at the pier, supported by local people and holidaymakers.
Earlier Gardai, local volunteers, the Coastguard and friends of the teenager’s family walked the shoreline at Rathmullan and Buncrana.
An all-weather life boat had been launched but gale force winds and heavy rain hampered the operation.
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