Erin Brockovich -- The Mug Shot ... And It's ROUGH [PHOTO]

Erin Brockovich's new mug shot is pretty rough and pretty shocking ... but that's what you get when you operate a boat wasted ... allegedly.

TMZ broke the story ... Brockovich was popped over the weekend for operating a boat under the influence.

A Nevada game warden spotted Brockovich struggling to dock her vessel at Lake Mead ... her BAC was nearly double the .08 legal limit.

Brockovich apologized this morning ... insisting she didn't endanger anyone because she wasn't boating in open waters -- just moving the boat "within its own slip."

"That being said, I take drunk driving very seriously, this was clearly a big mistake, I know better and I am very sorry,” she added.

We're told Brockovich is free on bail after briefly docking at the Clark County Detention Center.