Above is an interesting look at the inner workings of a MK VI patrol boat assigned to Coastal Riverine Group (CRG) 1 Detachment Guam, part of Coastal Riverine Squadron (CRS) 2.
The U.S. Navy Mark VI patrol boat is a very well-armed successor to classic PT boats of WWII (sans torpedoes), Nasty boats of Vietnam, and Cold War-era PB Mk IIIs. The Mk IIIs, a heavily armed 65-foot light gunboat, was replaced by the Mk V SOC (Special Operations Craft), a somewhat lighter armed 82-foot go fast and the 170-foot Cyclone-class patrol ships.
Now the Navy coughed up the idea for the Mk VI back in 2012, and plan on obtaining as many as 48 of these boats and are deployed in two separate strategic areas of operation: Commander, Task Force (CTF) 56 in Bahrain and CTF 75 in Guam.
At $6-million a pop, they are twice as expensive as USCG 87-foot WPBs and with much shorter legs, but they have huge teeth. Notice the 25mm MK38 Mod 2 forward and aft, the M2 RWS mount atop the wheelhouse, and the four crew-served mounts amidships and aft for Dillion mini-guns, M240Gs, MK19 grenade launchers, or other party favors. Of course, these would be toast in a defended environment like the China Sea but are gold for choke points like the Persian Gulf, anti-pirate ops, littoral warfare against asymmetric threats etc.
They also provide a persistent capability to patrol shallow littoral areas for the purpose of force protection for U.S. and coalition forces, as well as safeguarding critical infrastructure.
You know, classic small craft warfare dating back to to the Greeks.