naval, navel

Naval or naval means having to do with ships or sailors. Naval is the adjective ( describes something ) form of navy--
The president of the United States is commander of all the land and naval forces.
He applied to the naval academy at Annapolis after deciding on a military career.

Navel or navel means belly button--
They are called navel oranges because they have a belly button.
Many people think that philosophers are navel gazers, who sit and stare at their own belly buttons and chant omphalos.

Now that you know that, you can say--
"Naval stores and provisions should include navel oranges, to prevent scurvy."