The jet skier was reported to be on the East side of Brownsea, in the area known locally as Brownsea Roads.
Conditions in the harbour were squally, with a gusting south westerly wind F5 and moderate visibility.
The lifeboat volunteers were soon on scene and recovered the casualty, he had at this stage regained consciousness, however it was believed that he had been in the water for some time. The lifeboat crew carried out an assessment and a crewmember transferred across from the D Class to help administer casualty care, the lifeboat radioed the Coastguard to request that an ambulance attend the lifeboat station.
Meanwhile, the D class crew checked that the other jet skiers, who were in the party, were okay.
The casualty was made comfortable in the Atlantic and brought back to the station where he was transferred into the care of the paramedics and a critical care practitioner from Dorset and Somerset Air Ambulance to get checked out at hospital.
Both lifeboats were back at the station, washed down and made ready for service by 3pm.
This was the first call out of the New year for Poole Lifeboat volunteers.
The RNLI charity saves lives at sea. Its volunteers provide a 24-hour search and rescue service around the United Kingdom and Republic of Ireland coasts. The RNLI operates 238 lifeboat stations in the UK and Ireland and more than 240 lifeguard units on beaches around the UK and Channel Islands. The RNLI is independent of Coastguard and government and depends on voluntary donations and legacies to maintain its rescue service. Since the RNLI was founded in 1824, its lifeboat crews and lifeguards have saved over 146,000 lives.