A number of sub-aqua clubs from Athlone, Mullingar and Roscommon were training together when the incident occurred just before midday on October 10.
It is understood that a young diver from County Roscommon became ill after completing a rapid ascent from 14 metres of depth.
Diver first responders and a medical professional who happened to be on site administered first aid at the scene for suspected decompression sickness before the arrival of the ambulance service.
Sligo’s Search and Rescue Helicopter, Rescue 118, was also dispatched and Coast Guard volunteers, assisted by local divers, secured a landing site for the craft.
The diver is not thought to have been too seriously impacted but was taken by helicopter to the National Hyperbaric Medicine unit based in Galway University Hospital for treatment.