In article , says...

Normally the term "boat" is reserved for submarines in the Navy, but
there were a few small ships that were also referred to as "boats".

This one is a PG or "Patrol Gunboat" of the Vietnam era. One of
the most unique and exciting ship (or boat) that I served on in the
Navy.

I posted this pic and story on Facebook a couple of years ago, but
thought some might be interested in what it could do. The following
is a narrative of my first experience underway on the USS Surprise.
Tiny link at bottom is to a picture of the ship/boat:

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These Patrol Gunboats were designed for coastal operations during the
Vietnam Era. The ship had an overall length of 165 feet with a 24-foot
beam and displaced approximately 250 tons. Power was provided by two
variable-pitched propellers which are driven by a combination of two
diesels at low speeds and a gas turbine at high speeds.

Top speed was well in excess of 35 knots (40+ mph). It was capable
of going from stopped to full speed in about a minute and then from
full speed to stopped in less than it's own length. This maneuver is
known as a "crash-back".

My first day on the USS Surprise involved performing a crash-back. I
happened to be on the bridge when the young Captain gave the order to
"prepare for crash-back". I asked what a "crash-back" was and the
Captain explained that we would go from full speed to stopped in less
than it's own length.

I looked out one of the bridge windows. At over 35 knots, this 250 ton
ship was behaving like an overpowered outboard boat. It leaned into
it's turns and was skipping over the ocean waves with a slap-slap-slap
sound. I turned to the Captain and said, "No freakin' way".

Basically what happens is the pitch of the two props is instantly
reversed while the gas turbine engine remains at full throttle.

The countdown began. 10-9-8-7 ....
then the order came ... "Crash-Back!"
The Captain tossed a small cardboard box out of a bridge window at the
moment of the Crash-Back order. It never reached the fantail of the
ship before we were stopped and were actually starting to move
backward.

For the late 60's I think these ships/boats had beautiful lines.
Link to pictu

http://tinyurl.com/q4vs2cp

I got to tour one of those back in about 70 in Pearl Harbor. The engine bay was huge.