A Wellington man has described his frantic rescue efforts in an attempt to save a drowning woman.

The woman died after getting into difficulty while diving with her husband in Owhiro Bay yesterday - the third drowning off Wellington's south coast this summer.

The man, who doesn't want to be named, saw the pair from his house and ran down to them on the shore where her husband had already paddled her to the side.

The man says the husband was "blowing in her mouth" while he "held her and started compressions."

The man says the arrival of a third man made things easier as they could support the woman and perform CPR better.