There was some pretty concrete evidence of why Kubiwhatever can't cut Kimi in his match against Zabuza. I'm gonna go find it.
As for the drowning argument: The entire body drown has been disproven seeing his fight with Gaara. As for Suigetsu invading Kimi's body and drowning from the inside (which he hasn't shown being capable of but whatever...) teeth are, chemically, very very similar to bone. He could just create a mouth guard by fusing all his teeth together to create a solid wall.
Last edited by White Silver King; July 11, 2011 at 10:17 AM.