Article: People can't survive for more than three or four days without fresh water. Go inland and try to find a water source from a stream or waterfall on the island. If it's completely barren, then you'll need to create a solar still and take advantage of rainfall when it occurs.  A solar still uses the sun to create condensation. Dig a hole in the ground and put a container at the bottom. Surround the hole with wet leaves, then put a large piece of plastic down over the hole and weigh it down. Condensation will collect in your container and you'll be able to drink it.  When it rains, make sure that you are filling up containers to catch the fresh water to keep you hydrated for the long run. Boil the water before you drink it. Check for water at the base of leaves or cacti, inside of caves, hollowed trees, or undercut banks.  You can also get water from coconuts, cacti, or other plants and fruits.  Collect rainwater in buckets, plastic containers, bins, or garbage cans. Heating the water above 185° F (85° C) for three minutes will kill all pathogens in your water.  Severe dehydration could cause low blood pressure, rapid heartbeat, rapid breathing, delirium, or unconsciousness.  Do not drink salt water from the ocean because it will dehydrate you. While your body is capable of surviving one to three weeks without any food, not eating will weaken you, and it will make it harder to do other things that are required to survive on a desert island. Eat fruits and vegetables that you know not to be poisonous like coconuts, bananas, and seaweed. Avoid potentially poisonous, unknown berries. Scurvy is a serious condition that occurs when you don't have a balanced diet. Symptoms include fatigue, anemia, and infections and is caused by a vitamin C deficiency. Eating fresh citrus fruits like lemons and oranges can help prevent the condition. The protein and nutrients from meat and fish will give you energy. Mollusks, clams, oysters, crabs, muscles, and fish are all things that you may be able to find in the shallow waters surrounding or on an island.  You can sharpen sticks and hunt small reptiles, fish, or birds in the isle as well.  If you're having trouble catching or trapping bigger game, locate slower moving insects that you can eat that live in the desert like beetles, spiders, and centipedes.  Cook shellfish thoroughly before consuming it. Bacteria could cause you to become ill. If you cannot create a makeshift fishing pole, then sharpen a long branch or stick to make spears that you can use to go spearfishing. If you've never eaten the fruit that you find on the island, test it for poison by rubbing it on a sensitive part of your skin, like your wrist. Wait 45 minutes. If there is no adverse reaction, rub some of the food on your lips. If you form a rash, or there is burning or irritation, then the food is most likely poisonous. Never eat large amounts of any unknown food. Eat a small amount, wait an hour or two to see if you feel sick, then eat the rest of it. Beware of fruit that smells like peaches or almonds as it could be poisonous. Do not waste anything, even if you have an overabundance of it. Store away your excess food and water and stick to strict rationing.  The body requires 32 ounces of water a day and 200-1500 calories of food for an average person. Try to ration as much as possible without becoming dehydrated or malnourished.

What is a summary?
Find a fresh water source. Collect food from the plants on the island. Hunt for fish, insects, and small animals for food. Test the food you eat for poison. Ration all of your supplies.