Nevada Department of Wildlife spokesman Edwin Lyngar says Brockovich was arrested late Friday night after breath tests showed her blood-alcohol level was just over twice the legal limit of .08.
A game warden noticed she was struggling and needed assistance while trying to moor her motor boat at the Las Vegas Boat Harbor near Boulder City.
Lyngar says she had been out on the boat with a male companion but was alone when she tried to dock the boat.
The 52-year-old Brockovich didn't immediately respond to a request for comment.
She was released from the Clark County jail after posting $1,000 bail.