Unused ship time cannot be carried forward into a subsequent calendar year.
The Office of Naval Research has expressed the following policy:
"When a Principal Investigator funded by the Oceans, Atmosphere and Space Science and Technology Department wants to schedule a cruise on any ship in the University-National Oceanographic Laboratory System, they must fill out a UNOLS Form 831 Ship Time Request (on the web). Once the cruise is scheduled on the requested ship, the Marine Operations Office of the university that operates the ship will submit a proposal to the Research Facilities Program. In the case of SIO the Ship Scheduling Office at SIO will submit proposals for ship time and technician time for all ONR funded cruises [aboard Scripps-operated research vessels].
If any Principal Investigator has not used ONR funded cruise days in any given calendar year, these days will be converted to dollars and put as carry-forward on the ship time proposal for the following calendar year to ONR."
In other words, the funds associated with unused ship time remain at Scripps to be used the following year, but they will not be associated with the original Principal Investigator (PI). They instead will be applied toward whatever seagoing research is conducted by ONR in the following year. There is no obligation of this time toward a particular PI or project.
The policy of the National Science Foundation (Ocean Sciences) is essentially identical.
The cost of ship time changes each year, and the cost of a ship day in Year 1 will be less than in Year 2 [usually]. A PI may not "bank" their unused time to be used in a subsequent year.
A PI with wishes to reschedule unused ship time from one calendar year into the next must obtain new approval from their sponsoring scientific program manager. The program manager will then interact with their agency's ship operations program (either the Research Facilities Program at ONR, or the Ship Operations Program at NSF). Once approved at the agency level, the PI should submit a new UNOLS Ship Time Request, and the new ship days can be assigned by the Scripps Ship Scheduling Office.
Questions? Contact the Scripps Ship Scheduling Office at firstname.lastname@example.org or (858) 534-2841.