Military members may be entitled to extra pay, depending on the circumstances. These special pays are subject to income tax, unless earned in a designated combat zone. Military members performing sea duty are entitled to an extra monthly pay, called "Career Sea Pay."
Sea duty, as defined by an entitlement to career sea pay, is service performed by a military member under orders issued by competent authority.
You are eligible for Career Sea Pay while permanently assigned for duty to a ship, ship-based staff, or ship-based aviation unit and serving in a ship whose primary mission is accomplished underway. You are also eligible for Career Sea Pay if you are temporarily assigned to duties ashore (TAD), and sea duty continues for the first 30 consecutive days from the beginning of the TAD. This means you are are permanently assigned to a ship, but you perform duty ashore for 60 days; thus, the first 30 of those days would still count as sea duty, for the purposes of receiving Sea Pay.
You are also eligible for Career Sea Pay while temporarily assigned for duty to a vessel, ship-based staff, or ship-based aviation unit and serving on a ship whose primary mission is underway.
Career Sea Pay also applies while you are permanently or temporarily assigned for duty to a vessel or ship-based staff, and serving on a ship with a primary mission accomplished in port, but only during that period while the ship is away from its home port.
A ship is considered away from its home port whenever it is at sea, or in a port located more than 50 miles away from the home port.
Finally, Career Sea Pay may be available to you if you are serving as a member of the off-crew of a two-crewed submarine.