I haven't been able to determine exactly what causes it, but it seems like about 60% of the time a Drood exits a crew compartment and touches water, the Drood falls through it as if the water isn't there. These Droods can walk around on the sea floor, but when not touching the ground the swimming animation still plays, and the physics acts very strangely (I think the velocity vector is stored relative to the direction the drood is facing, so when the drood looks a different direction it starts moving a different direction at the same speed).
