US Navy (USN) Sailors assigned aboard the USN Arleigh Burke Class (Flight I) Guided Missile Destroyer (Aegis), USS MILIUS (DDG 69), armed with M9 9 mm training weapons equipped to fire simunition rounds, and wearing paintball protective face masks, prepare to advance through a watertight door during training at the Center for Security Forces at Naval Station (NS) San Diego, California (CA)