You've somehow struck lucky and found an island that has an abundance of fresh water and sustainable food supplies, offering a healthy balanced diet (provided you're not allergic to fish, coconuts etc).
My question for you:
Do you spend your time making yourself comfortable and hoping nobody will ever find you (chances seem high, as anywhere else in the world habitable like this is populated) or do you start building a raft to escape back to the civilised world?
Invent your own reasons for how you got there; ship wreck, took a wrong turn in the deep end of the local swimming baths, aliens... I don't care. What I want to know is, what do you do?