For me, it'd be kinda tricky. Knowing that there would be no wi-fi there at all would terrify me. I suppose I could bring a bottle with paper and pen (I hope this counts as one item?), and write out my request to be rescued, and just let the waves carry the bottle wherever, as long as it gets to someplace where people could call for help for me, y'know? D:

I'd also bring a jug of water and some apple seeds, just in case I would want to grow my own fruit and whatnot. I'd also use that jug of water for hydration purposes as well. It's always nice to at least try and grow a farm when you're stranded in the middle of nowhere waiting for help, it's the least you could at least do for yourself, after all. xD