Laying on the floor... using your back muscles (just the opposite of what I told Mania ) pull your knees up slightly off the floor. That is the position you want underwater.
Pull your toes down so that the bottom of your foot is at a right angle to your lower leg and keep your lower leg at a right angle to your upper leg. That is the reference position you want underwater.
I say reference because you may at times need to move your feet further back to counter any tendency to topple over onto your head. Your feet/fins are a weight balance that can be adjusted back and forth to keep you in trim.
Pull your toes down so that the bottom of your foot is at a right angle to your lower leg and keep your lower leg at a right angle to your upper leg. That is the reference position you want underwater.
I say reference because you may at times need to move your feet further back to counter any tendency to topple over onto your head. Your feet/fins are a weight balance that can be adjusted back and forth to keep you in trim.