The 25-year-old starts a two-month crash course with the Royal Navy on Monday that will send him patrolling the Caribbean Sea onboard the frigate HMS Iron Duke.
Serving as Sub Lieutenant Wales, William will be expected to take part in the full range of naval officer duties – including boarding suspicious vessels and searching them for drugs.
"It will be down to the discretion of the commanding officer. But it's hoped he will take part in all aspects of life on board," explains Rear Admiral Bob Cooling, assistant chief of the naval staff. "He might even be armed as a precaution."
As William's deployment takes place during the height of the hurricane season, his other main job will be to provide humanitarian assistance in the event of a natural disaster.
But it will be no luxury Caribbean cruise: the Prince will bunk alongside regular naval officers and be expected to take part in four-hour watches throughout the night.
"He will keep exactly the same daily routine as any junior officer on board," adds Cooling.
"He will bunk with other young officers – probably in a four-berth cabin. It is not an en-suite so he will be making the walk up the passageway to the heads just the same as any other young officer does."
Before he boards a ship William will also have to pass the Navy's Basic Sea Safety Course, which involves firefighting blazes reaching 400 degrees in cramped, enclosed environments and learning to safely abandon ship.
"The training will be very rigorous," Cooling says. "He will need to be able to pull his weight in an emergency, so that he's not putting himself or other members of the ships company at risk by being a liability."
After his turn on the HMS Iron Duke, Prince William will return to the Household Cavalry to continue his army career.