Unlike police, Coast Guard officers say they don't need probable cause. They can climb aboard any boat, at any time, in US waters.
"You'd be surprised how often we see people actually just drinking beers, just out in the open," according to Nick Kimose, of the US Coast Guard.
Like police, the Coast Guard carries breathalyzers, and can test for blood alcohol levels.
In California anything over 0.08% is deemed illegal, whether on land or sea.
Last year US Coast Guard officials logged 672 deaths from fatal boating accidents. 1 in 5, they say, was due to alcohol.
"Drinking and driving on a boat is just as dangerous as in a car, I believe," says Chris Sommers, who works at the Dana Point Fuel Dock.
Sommers says he has seen his share of intoxicated boaters from the fuel dock where he works.
It's why the Coast Guard will be out in force beginning Thursday with what they call a "substantial presence" as part of their Operation Dry Water program.
Local news from across Southern California
They will partner with local sheriff departments and cruise the coast line from Dana Point to Morro Bay.
Experts say boaters may not realize how the things they love, wind, sun and motion actually increase the effects of alcohol.
"You're on the water, but its a motor vehicle, and it's just as dangerous," according to Kimose.
Mitchell Margaretich has been a captain for 25 years. He says it's the harbor where boaters really need to be cautious.
"There's a million little kayakers, so you have to be aware," according to Margaretich.