Brockovich, who was portrayed by Julia Roberts in a 2000 movie about her fight over the pollution of a California town, was arrested late Friday night on suspicion of boating while intoxicated. She is free after posting $1,000 bail.
Authorities say a game warden noticed the 52-year-old Agoura Hills resident was struggling and needed assistance while trying to moor her motor boat at the Las Vegas Boat Harbor. Brockovich had been out on the boat with a male companion, but she was alone when she tried to dock it.
Officials say Brockovich's blood-alcohol level was just over twice the legal limit of .08. She apologized for her actions in a statement released Sunday, but stressed that she did not operate the boat in open waters.
"At no time was the boat away from the dock and there was no public safety risk," Brockovich said. "That being said, I take drunk driving very seriously, this was clearly a big mistake, I know better and I am very sorry.
The Associated Press contributed to this report.