I can't imaging anybody diving without using their hands to break the water. It is just too hard on the face as the water rips at the eyes. I have never seen anybody do this unless they were doing upside down cannon balls.

The simple answer is, No, this was not injurious. Your neck would have been at greater risk if you did hit hard enough to traumatize the brain.

I honestly think you are stretching things a bit. The slap of the water would not feel good to your skin and face.