South King Fire and Rescue says a crew responded to a report of a diver down shortly before 7 p.m. Saturday at the Redondo Pier in Des Moines.
A news release says a dive partner first tried to help the stricken female diver while both were under water, but failed.
Working with the partner, the rescue crew was able to locate the diver and bring her to shore.
Fire officials say resuscitation began right away, but the diver was pronounced dead at the scene.
Fire officials say initial reports were that the diver had run out of air, but rescuers have not confirmed that or determined the cause of the accident.
No other details were released.