If you were stranded on a deserted island, what one thing would you bring with you and why?

Gosh...that's really hard. I suppose a phone with WiFi connection so I could phone início wouldn't be very realistic...XD Well...my first thought was to bring my drawing stuff like my sketchpad and pens so I could draw all the animais and birds on the island (and write messages to put in bottles), but thinking about it they could easily run out/become damaged over time, and I could probably find natural pigments and stuff on the island and draw pictures on rocks and things. So I'd probably bring a musical instrument that I could play (or at least know how to play), like a piano or a harpsichord. I could get really, really good at playing the piano and create elaborate compositions without anyone disturbing me. Sure, I wouldn't have any comida and water, but I'd be one heck of a pianist XD I could then scratch the notes as sheet música into the walls of a cave or rock, and when people would come many centuries later they could see the notes and write them down for other people to play. Maybe it wouldn't save my life, but if I was to be stranded on an island I'd at least like people to know I was there.

A bridge back to the main land.