Since I had tethered the camera on my left side, it got tangled with my BCD inflator hose and started interfering with my snorkel as well when I let go of it so it floated up. And it was just ever so slightly positive; it rose gently and slowly when I let go of it.
After that experience, I'm not carrying anything that's positive. Except for a dSMB in the few fractions of a second after I've inflated it and before I release it.
EDIT: I've just formulated Storker's 1st rule of SCUBA gear: If it isn't negative, it will cause entanglements when you're not holding it.