Police are trying to work out how a woman ended up in the water at Douglas marina in the early hours of Sunday morning.
The emergency servies were called out at around 1.40am.
Officers got her out of the water, then she was lifted from a boat to the harbour side with the help of the Fire Service and taken to Noble's hospital.
Inspector Derek Flint says a well coordinated rescue meant she was transferred to hospital at the earliest opportunity.
They are now trying to establish how she ended up in the water, and want to speak to anyone who was in the area around that time.
Call police on 631212 if you saw what happened.