Kanye West Kinda Says in 'Vultures' Song Bianca Performed Oral Sex on Venice Boat

Kanye West has blown the lid off the water taxi mystery in Italy a few months back ... he seems to confirm, it was indeed oral sex.

Kanye's new song "F**k Sumn" reveals what and who went down when his wife, Bianca Censori leaned down as Ye's pants were at least partially down.

The telltale lyric ..."Shawty wanna f–k on somethin’? / F–k on me / Suck on me, publicly."

As you probably recall, Kanye and Bianca were mum back in August as to what was really going on, but the water taxi company felt it knew of the shenanigans ... it banned K&B from its vessels.

As you also know, Kanye and Bianca caused a stir with what she was wearing around Venice ... more accurately what she was not wearing.

Kanye collaborated with Ty Dolla $ign for the song, which dropped Friday.