Watch Standing

A ship operates 24/7 and some personnel stand watches on the Bridge, Engineering, Radio, Combat Information Center and other spaces in addition to their regular ships work.
Watches are usually 4 hours long.  To provide watch rotation, sometimes the Dog Watch is split

Mid Watch -  Midnight to 4 AM (0000 - 0400)
Morning Watch - 
4 AM to 8 AM (0400 - 0800)
Forenoon Watch - 
 8 AM to Noon (0800 - 1200)
Afternoon Watch - 
Noon to 4 PM (1200 - 1600)
First Dog Watch - 
4 PM to 6 PM (1600 - 1800)
Second Dog Watch - 
6 PM to 8 PM (1800 - 2000)
First Watch - 
8 PM to Midnight (2000 - 0000)

Bridge Officers

Nothing happens on a ship without permission of the OOD (Officer of the Deck).  During his watch, he is in charge of every function of the ship.  Basically, his job is to carry out the Captains orders and he oversees the running of the ship for the captain.

The JOOD (Junior Officer of the Deck) is an under instruction Jr officer and is specifically charged with the actual driving of the ship under the direction of the OOD.

Conning Officer
The Conning Officer is the only person allowed to give orders to the helmsman.  Under normal conditions the JOOD is also the Conning Officer, but at other times a specific Conning Officer may be assigned.  For the ship's safety the OOD or Captain may "assume the Conn" and any time.

Helm Safety Officer
During restricted maneuvering (entering, leaving port, underway replenishment, etc) a Helm Safety Officer is posted behind the helmsman.
This is usually a Jr. Officer working on his OOD qualifications.  He is a second set of eyes.  His job is to listen to the helm and engine orders and insure that the helmsman and lee helmsman carry them out correctly.

Enlisted Bridge Personnel

Quartermaster of the Watch (QMOW)
The QMOW is the senior bridge enlisted watch stander.  Maintains the ships navigation plot.  Maintains the general deck log and bridge-to-bridge radio logs.  Performs local weather observations, maintains weather logs and generates weather messages.   Provides advice to the OOD concerning issues of navigation and rules of the road. A QMOW is qualified in every enlisted bridge watch station.

Boatswain (Bo's'n) Mate of the Watch (BMOW)
Organizes and oversees the bridge watch standers.  Using his Boatswain's Pipe, passes information throughout the ship.

Actually steers the ship using compass and gyro heading, taking orders from the Conning Officer.  During normal steaming, this is a deck seaman.  During times of restricted maneuvering it is a qualified Master Helmsman.

Lee Helmsman
This person operates the Engine Order Telegraph,
taking orders from the conning officer.  He maintains communications to Main Control for engine and shaft RPM orders.  During normal steaming, this is a deck seaman.  During times of restricted maneuvering it is a qualified Master Helmsman.

Master Helmsman
This is a specially qualified helmsman. (Usually a Quartermaster) He is is fully qualified on Helm, Lee Helm and After Steering and is able to steer within 1/2 degree no matter what the sea state or situation especially during Restricted Maneuvering.  (Replenishment, Special Sea Detail, etc.)

In-port Quarterdeck Watch

A ship operates 24/7 even when in port.
A duty section represents a cross section of the crew and in an emergency can get the ship underway.

Command Duty Officer
On his day of duty is the senior Officer of the Duty Section and represents the Commanding Officer in his absence.

As underway, nothing happens on a ship without permission of the OOD (Officer of the Deck).  In-port the watch is shifted to the quarterdeck where the OOD over sees security and controls who comes aboard a ship. Usually the in-port OOD is an E-7 or above, however fully qualified E-6 or E-5 may also stand the watch.

Usually an E-4 or E-5, the Petty Officer of the Watch provides security on the quarterdeck and is armed with a side arm.  He is also responsible for keeping the deck log.

Usually an E-3 and below, the Messenger of the Watch is like the name says - He answers phone, runs errands for the OOD and performs "Wake Ups" as directed.