See the kind of training the US Navy Seals pass through

 

This photo shows one out of the several rigorous training the United States'Navy SEALS pass through.They are submerged under water with their hands tied behind their back and they have to pick up the masks with their teeth and swim out....
They are an exclusive band of about 2,400 special operators famously responsible for the 2011 midnight raid that led to the capture of Osama bin Laden.

This is a small compared to what our own Police forces go through...