What I've heard is they do/did a lot of explosive breaching. Then things like recoilless rifles, heavy machine guns or if you use a .50 caliber sniper rifle might further contribute to the situation.

I'm not sure if these types of units usually dive that deep that you would be worried about brain damage, but I'm less familiar with that side of things. Diving probably hasn't been that much of a focus during the recent years in the middle east either.