Survival Anything and everything

Survival. You alone on a desert island, where you haven't chance to communicate,
so you have to try to survive,
you only have an object,
what object do you have and why?

a well polished knife

a knife allow you to create tool or hunt to survive. and well polished in order to be able to reflect the sun with the blade. if a plane or boat pass abroad, it will be easier to be seen

is it a desert Island (only sand and really hot) or a deserted Island ( remoted and far away from civiliation) ?

Remoted and far from civilization