If I were to spent one month on a deserted island alone, I would have to bring a waterbottle. If there are no lakes, streams, or pools of water, and if the island has no seasonal supply of water, the only way to obtain water is by taking it from trees or any kind of NON-POISON plants...obviously. Coconuts are a good example, there is juice inside them, and it is very nutritious, and refreshing, Yum. By the way, deserted islands are usually uninhabited, but there are a good lot of plants and NEVER let a coconut drop on your head, obviously... The second item I need to bring are signal lights and flares or anything to make people spot you when they come to rescue you. The third item is a knife, it will help you in cutting or whatever, basically in survival there are quite a couple of things you are are not strong enough to do. The fourth item is a first-aid kit, you WILL get injured. The last item is an inflatable rubber dingy. Escape from a deserted island is your number one priority. You also need oars. Deserted islands are in tropical oceans which have lots of busy shipping lanes, hopefully a ship will spot you so you need the flares. For food you need to do what you must to survive. Tidbits or any kind of food will not last for a week without proper storage. If you want to save the lives of the food animals ( what have they done to deserve to get eaten, poor animals ) , fruit and edible plants are the best substitution. PS. If you bring a mobile phone, there will be no transmission. Besides, you have no need for electronics, they will not last. PSS. Courtesy of Man vs Wild for the information. Timothy Timuari.