It would act like the tail on a kite, but a very heavy one. If you were at max altitude and cranked the yaw full over and held it there, you'd hit the water really hard and probably do some serious damage to yourself, but I doubt if even then you'd manage to get yourself anywhere close to a horizontal attitude before impact. Your working against both the weight of the tail, the weight of your body and the stiffness of the tail.

I gotta be honest with you though, the immediate thought that went through my head the instant I saw it was I WANT ONE!!!!!!