1. For the split second it levels off before dropping like a rock do you jump? People have been jumping and diving from much higher positions for FUN for a while now, so I don't believe the distance is dangerous whether you go feet first or "dive" position. You do possibly risk having a helicopter land on you or even worst a blade catching you mid air.
2. Hang on and go down with the choppa, basically stuck in a "sitting position". You hit the water and due to displacement your body gets compressed like a car in a crushing machine.
I think if I had the right mind at the very second I would do option #1.
I could choose poorly, but that is what I am going with.