The 26-year-old was helped ashore by members of the public after getting into difficulties at a beach near Balmedie, Aberdeenshire, and rushed to hospital.
The area is near where the controversial tycoon Trump's links course is based.
An RAF rescue helicopter from Lossiemouth took the woman to Aberdeen Royal Infirmary.
The helicopter had been close to the scene transferring a sick offshore worker to hospital.
The area has hazards for swimmers, with a soft sandy shelf in the waters, which can catch out the unwary, and sand-bars. There are also dangerous tides.
A report will be sent to the procurator-fiscal.