Head Positioning

One more thing I neglected to mention about my head positioning. I try to look about a few degrees forward of the vertical, and press the head and chin down. In that way, I know the water is not flowing over the back of my head which creates drag. When the water hits my forehead, my head is cleanly cutting through the water which is optimal.
I also use my ears as feedback that my head is completely submerged in the water. If I hear water gurgling, then I am too much on the surface, or maybe even my ears are out of the water and then my butt is dragging. So I make sure that I hear no gurgling at all and then I know my head is deep enough.
Sprinted 1:40 for 100m today – got a sprinting test on Friday of 5x100m at 5 seconds rest…yikes!