A teenage scout who was swept into the sea fell around 45 feet after reaching the door of the coastguard helicopter sent to rescue her.
An Air Accident and Investigation Unit Ireland (AAIU) report into the circumstances surrounding the death of Aoife Winterlich (14) described the desperate attempts to save her life.
It found that the winchman who opted to lift her and a second teen out of the water simultaneously made a "sound decision".
Aoife, from Walkinstown in Dublin, was with her scout troop walking along the coast at Hook Head, Co Wexford, when she was swept into the sea, alongside a boy.
The male teen stayed with her and told investigators that she was unresponsive from shortly after they entered the water.
The Irish coastguard centre in Dublin received a call at 2.04pm and was told that a "number of kids" were in the water and a helicopter from a Waterford base was dispatched. The crew arrived on the scene minutes later, at 2.13pm, and a winchman entered the water less than a minute later.
When he reached her, Aoife was "pale and unresponsive", he told investigators. The second teen was supporting her, anxiously keeping her head above water, despite the risk to his own safety. Investigators praised the teenager for his "exceptional effort".
"The winchman was also concerned that if he winched one casualty to the helicopter, that the other would not be able to remain afloat until he returned," the report stated.
When deciding to winch both to safety together, he "considered that his only option".
However, as the winchman and the two teens reached the door of the helicopter and were about to be saved, Aoife slipped through the strop (a type of harness) and fell approximately 45ft into the sea. She was in the water for 31 seconds after the second fall.
The winchman immediately returned to the water and got her to the helicopter.
Afterwards the crew spent time looking for a third casualty in the water before the male teen told them there had been only the two of them and the helicopter then made its way to hospital.
The AAIU noted that due to the high-risk nature of rescue operations "there is always the possibility for a scenario to develop that has not previously been trained for".
It also highlights that there is no specific guidance on winching an unresponsive casualty from the water and the unit has recommended that guidance be prepared for all search and rescue teams about the risks associated with winching casualties.
Aoife died in hospital a number of days after the incident, on December 10.