An incredibly stupid question.
You pick the desert island for half a year with Irock. Upon landing on the island, you immediately kill Irock, thus gaining some food, and bones which may help creating a shelter. Afterwards, you tie what remains of Irock's body to a tree, with luck, a passing boat will see the dead body; and will go to check it out, thus giving you a chance to leave the island before the half a year is up.