{blackbabes} Venus Williams -- Booze Cruise Karaoke Jam

Venus Williams got her karaoke on in front of a cruise ship full of screaming fans of the band 311 ... and we've got the whole thing on video -- choreography included.

http://www.tmz.com/videos?autoplay=true&mediaKey=eb195bd9-b776-4953-acee-b363262ca94e

TMZ obtained footage of the awesome performance shot last week on a Carnival Cruise in the Caribbean, hosted by 311. In the clip, Venus and two friends are singing "You Wouldn't Believe" -- and they even threw in some dance moves.

Turns out Venus' group was randomly chosen to be in the karaoke contest -- which was judged by 311's lead singer.

Checkout the video ... the tennis ace definitely scored with the crowd.