Boating under the influence (BUI) can happen in a lake, a river, or on the ocean. Operating a boat or any watercraft while under the influence of drugs or alcohol (at or above a blood-alcohol concentration, or BAC of .08%) is much like driving a vehicle while under the influence: it is a criminal offense in the state of California.
The Harbors and Navigation Code does not prohibit passengers or the operator of a boat from drinking alcohol or carrying open containers in the boat like the vehicular codes do. In spite of this, a BUI offense is almost identical to that of operating a car or truck with a BAC at or above .08%. Details of this can be found in California Harbors and Navigation Code Section 655 at the following link:
This code includes a BUI when on a wakeboard, water ski, or sky ski and the procedures the officers will conduct are the same tests as with a vehicular DUI: field sobriety tests and breath or blood testing.
So next time you hop on that wakeboard after a couple beers, remember that you can be arrested for a BUI offense.