Bobbi Kristina drowned in her bathtub ... and the word 'drown" is critical.

TMZ has obtained the police report in which an officer writes they responded at 10:25 AM Saturday in reference to a "drowning."  

"Drowning" typically means someone died underwater. As we reported, Bobbi Kristina's husband and friend administered CPR after they found her face down in the bathtub and paramedics were able to revive her.

As we reported, Bobbi Kristina's brain function was "significantly diminished" and doctors told the family it didn't look good, although thankfully it got a little better Sunday.