Below is an extract from the newly released Ultimate Survival Manual. Rich Johnson is a former paratrooper and demolition officer, who once survived in the desert wilderness for a year, living in a cave and eating insects.
Find drinking water at sea
Water, water, everywhere -- and not a drop to drink? Not if you're prepared, resourceful, and willing to put effort into collecting drinkable water. And you should be: It will save your life.
Outfit your vessel with a plastic tarpaulin to catch rainwater and drain it into containers, allowing the first drops of rain to wash the salt off the tarpaulin. If you don't have a tarpaulin, use fabric to absorb moisture, then wring it out into containers. Never drink saltwater—it will make you ill and speed dehydration and death.
Pull a "MacGyver"
When you've been adrift at sea for a period of time, all your clothes end up encrusted with salt crystals. At the first sign of rain, give all your clothes and other fabric a seawater bath. Yes, it's salty, but not as salty as the salt residue, which will make any water it contacts undrinkable.
If you have sails, make a bowl out of them to capture the water. Tarps, shirts, plastic sheets, and even the raft itself can all collect water. Any can, bottle, or other container can store it. The first water you collect will have a high salt content, so store it separately, and use it to clean wounds or to wash food before eating.
Orient yourself by the stars
Seek the North Pole
To find Polaris, the prominent star that's close to the north celestial pole, look for the famous pattern of stars called the Big Dipper or the Plough in the constellation Ursa Major. Mentally draw a line connecting the stars at the end of the Big Dipper's "bowl," then extend that line out five times its length to arrive at Polaris. It's hard to miss, since it's the brightest star in Ursa Minor, or the Little Dipper.
Seek the South Pole
Traveling below the equator? Find the Southern Cross's long axis and extend a line down four and a half times the axis length. Then locate the bright stars Rigil Kent and Hadar to the left of the Southern Cross. Figure the midpoint between these two stars, then imagine a perpendicular line from that point to the end of the line drawn from the Southern Cross. That intersection marks the South Pole.
Catch fish in open waters
If you're in a life raft, small fish often gather beneath the raft, either out of curiosity or because they feel sheltered there. Who knows? But catching those fish might satisfy your need for nourishment. Troll a hand-line with a hook and anything flashy to serve as a lure. Jig the lure up and down a few meters below the surface, being careful not to snag the life raft with the hook. After catching a fish, use the guts as bait to catch more.
Avoid shark bites
Sharks don't usually hunt people as a food source, which is why most shark bites stop there: Once the shark realizes you're not a nice blubbery seal, it leaves you alone. Unfortunately, that little "mistake" isn't all that little for the human on the receiving end of those chompers. Here's how to avoid those nasty bites:
Cede the sea
While there certainly are open-ocean predators, most shark threats are in the shallows and near food sources. Coral reefs are popular hangouts -- and happen to be the most desirable dive sites. If you're diving in these areas, be aware of the shark risk before you enter the water, and dive with at least one partner, as sharks are less likely to mess with a group.
If you do suddenly find yourself in close quarters with one of these beasts, your best bet is to get out of the water, swimming away with smooth, even strokes that won't attract its attention.
Face your foe
When a shark wants to eat you, you'll know in advance: It will hunch its back, lower its fins, and rush at you in a zigzag. Thrust your spear gun, camera housing, knife, or whatever else you're packing to discourage it. If you can, punch its super-sensitive nose or stab at its eyes or gills.
Divers report successful evasion by descending to the seafloor and waiting for the sharks to leave. But that only works if you've got an air tank.
Right a capsized boat
Small sailboats capsize easily, but luckily, they're easy to right. Crawl up onto the overturned hull, grab the centerboard (keel), and lean back, using your weight against the centerboard as a lever to flip the boat over.
When it's upright, crawl aboard and bail out the water. If your capsized boat is a motorboat without a centerboard, righting it will take a bit more doing. Tie one end of a rope to something secure in the middle of the boat, like an oarlock. Toss the free end of the rope up onto the hull.
Crawl onto the hull to grab the free end of the rope, facing the side where the rope is tied. Back up toward the water and lean back, using your weight against the rope to pull the boat over. Once it's upright, scramble on and start bailing.
Put out a boat fire
A fire on a boat is a life-threatening catastrophe, so it's wise to have a plan in place before you leave shore.
Step one: Store fresh fire extinguishers in locations near the galley and the engine compartment, the two most likely locations for fire.
Step two: If fire breaks out, move everyone out of the cabin and get them into life vests. Call VHF channel 16 to report the emergency. Prepare to abandon ship.
Step three: Fight the fire with extinguishers, keeping a clear escape route behind you at all times. Always extinguish fires from the bottom up.
Plug a leak
Water is supposed to stay on the outside of a boat, but inevitably some gets inside due to rain or waves coming over the bow. That's not a big problem. However, when water invades because of a leak, the problem becomes quite real.
Find the trouble spot
Your top priority is to locate the leak. If you can't find it, head for dry land fast. Check to see that the boat's drain plug is closed -- if it's open, that's your culprit.
Heal your hull
If the leak is caused by a failed through-hull fitting, stop it with a conical soft-wood plug that should be tethered to the hull.
Protect with plastic
If the hull is fractured due to impact, place a large plastic sheet across the leak on the outside of the hull. Secure the plastic with ropes. Water pressure will help hold it in place as you carefully head for land.
Use old faithful
If all else fails, you can repair small cracks with duct tape.