If you put that into any journey planner, it will find an itinerary using the ferry timetable - i.e. using XOF for the Gosport-end ferry terminal. If you've wondered how that works, and what is possible, this is a quick description.
The "system" of data feeds includes three files to allow links that are not trains, one of which is a timetable file of what are called Z-trains (i.e. not trains at all, but links nonetheless). Even if a timetable isn't included, a JP can use the link based on a link travel time that allows for waiting.
The links are defined in one of two formats, old or new. The older format looks like:
ADDITIONAL LINK: WALK BETWEEN AHV AND NCM IN 10 MINUTES
The newer format is more structured and allows service times and days of operation to be added (it's likely that only this one is still used), e.g.:
M=METRO,O=MAN,D=MCV,T=8,S=0001,E=2359,P=5,F=07/01/2017,U=28/02/2017
The defined link types are:
BUS, TUBE, WALK, FERRY, METRO, TRAM, TAXI or TRANSFER
And that's all there is to it - surprisingly simple, though of course the Z-trains file itself is in the TTIS CIF format for rail timetables, which is orders of magnitude more complicated.