Excerpt from www.defencejobs.gov.au
http://www.defencejobs.gov.au/navy/jobs/SeamanOfficer/?entryTypeId=8 Junior Seaman Officers, as Commanding Officers' representatives, are responsible for the control and safety of Naval vessels at sea and alongside (in port). Their first major qualifications are the Navigation Watchkeeping Certificate followed by the Bridge Warfare Certificate. The Navigation Watchkeeping Certificate focuses on mariner skills and enables the holder to conduct a watch in a minor war vessel, such as a patrol boat. The Bridge Warfare Certificate enables the holder to drive the Navy's major warships, including frigates, as Officers of the Watch.
Seaman officers will have a number of different jobs that are designed to equip them for the role of higher management in the Royal Australian Navy. Seaman Officers are the only officers who can gain command of the Navy's ships and submarines. Once you've consolidated your skills as a Seaman Officer, you'll have the opportunity to develop your career with a specialist qualification including:
Mine warfare and Clearance Diving Officer (MCDO)
Maritime Geospatial Officers - Hydrography (MGO-H)
Navigation (N)
Principal Warfare Officer (PWO)
Meteorology and Oceanography (METOC)
Officers Submariner
The main role of the Seaman Officer is Officer of the Watch duty - "the officer primarily responsible for the navigation of a ship, in the absence of the captain, during a certain watch."
http://en.wikipedia.org/wiki/Officer_of_the_Deck aka Officer of The Watch
another excerpt
An Officer in charge of the Navigational Watch or Officer of the Watch (OOW) as we all know comprises the Bridge Team. On merchant vessels, the watch duty officer is always accompanied with a look-out who is also a helmsman. In case the officer of the watch is a newly promoted officer, he will be performing his duties on the bridge under the watchful eyes of the Captain.
What is the Officer of the Watch responsibilities?
The Officer of the Watch is the Master’s representative and responsible for complying and executing the master’s orders.
The OOW is responsible to the master for:
Safe Navigation of the ship
Safety of the personnel or crew onboard the ship
Safety of the environment and pollution prevention
Maintaining the required standards of good seamanship
compliance of COLREGS
Compliance with bridge standing orders and night orders
Keeping a proper look out at all times
The officer of the watch must be familiar with:
Government regulations
International conventions
Bridge Standing Orders
Master’s Standing Orders
The Officer of the watch is responsible for the safe navigation of the vessel even with the presence of the master on the bridge, until the time the master informs him specifically and in writing that he will take the command or the watch.
The Officer of the watch should keep his watch on the bridge until properly relieved.
He shall consult or ask the Master if he is in doubt of any interpretation or regulations or instructions, or if he has any doubts regarding the manner of which he is required to carry out his duties.
These are among the duties of an Officer of the watch. I’d like to point out something more about this matter, which I mostly notice on the bridge.
The role of the Officer of the Watch when the Master takes command of the ship
Most of the time I’ve noticed that some OOW would simply stand on the radar, drink a cup of coffee, but forgot the most important part of his job. You are on the bridge to check if the captain is giving the right orders on engine speed, rudder command, following the instructions of the VTS, and applying the COLREGS.
You are there to check that everything is under control. This also applies when the ship is under pilotage. Remember that the master has a lot of things running over his head. A lot of messages and telexes to send, and to answer. And you are the person that he shall depend on the bridge to achieve the safe navigation of the ship.
http://pinoymaritime.com/blog/2009/03/your-responsibilities-as-an-officer-of-the-watch/ Good Luck! I'm applying for that exact job in the RAN.