Tree of Life
Below coconut trees are taken from Alapuzha ‘The Venice of the East’ one of the best, most beautiful and world famous backwaters of Kerala.

Coconut tree is considered to be the tree of life. From root to head everything and anything could be used. Say the roots are used as medicine for dysentery and even sometime could be used as a tooth brush. The trunk is best known for salt resistance and are hard durable wood used to make small bridges, bench, table, roof and frames. The leaves are used as roofing materials when nicely weaved together to form sheets. Most importantly the coconut fruit is the nut/seed of coconut tree is high in protein where as milk is refreshing, light and low in sugar. Its an amazing natural energy booster ideally and highly recommended for fatigue.
I always wonder (those knowledge I acquire from movies) how coconut trees are grown in the most remote islands in the sea; because the coconut fruit floats readily and have been dispersed widely by ocean currents. The coconut palms flourish best close to sea with abundant sun and rain, for the best growth they also need to be in a highly humid environment.
If you are ever trapped in an island this is the tree you should be looking for. Climb up (if you can) and look out for any ship. Get some coconuts dry it and squeeze them to get some oil to be used as the best natural sunscreen or suntan lotion. The coconut fruit milk or water is the only fresh liquid you can manage to sustain your life, other than rain water. And yes the safest food you can get would be the meat inside the coconut. Once you are settled with enough food and drinks, and has no chances of any ships around; the best bet would be to start thinking and building a raft.