First one must imagine sailing during the early 18th century. Navigation was as much an art as a science. The compass showed north, and calculations gave a good approximation of the latitude (the distance north or south of the equator) but no one had yet figured out how to calculate longitude (the distance from east to west.) Because of this, it was impossible to ever tell exactly where you were.
Most navigators also used a version of navigation called “ded reckoning.” This worked by making notes to the effect of “we traveled northwest for 6 hours at about 7 knots, and then turned and traveled for 2 hours at about 4 knots.” Assuming that you knew where you were when you started and did the math right, you could figure where you were at the end of the day.
If you think this seems like a terrifyingly vague way to determine where you were you would be right. Add to this that many European ships were traveling to places that they had no record of, and you have a recipe for disaster.
Ships ran aground. This happened when the bottom of the bottom of the ship (like icebergs ship have a lot of their bulk underneath the water) hit the bottom of the sea (coral reef, rock outcropping or shore.) Because all this was happening underwater, it was hard to tell how deep the water under the boat was.
Ships tried to get information about the bottom of the sea by dropping a piece of lead coated with wax and tied to a string. Once the lead weight hit the bottom it would be pulled up and examined. The length of the string told how deep the bottom was, and whatever stuck to the wax gave an indication of what was down there… It might be soft sand or hard rock.
This system was far better than nothing, but a sudden change might leave a ship bumping along the bottom. If the ship struck hard enough, it might run aground.
A grounded ship was in trouble. Striking a hard surface would damage the bottom of the boat, allowing water to get in. This was when the ship’s carpenter might show his skills. A good carpenter might be able to plug any holed before the ship took on too much water.
But even if the hull was not damaged, or the damage could be repaired, the ship was now stuck. Friction with the sea bottom might prevent the vessel from moving.
The crew could do many things to get off the underwater hazard. In some cases a rising tide might simply lift the ship clear. But if the accident happened when the tide was already high, a receding tide might leave the ship literally high and dry.
Ships were not designed to hang in the air, supported at one point by a solid object, but with other parts dangling unsupported. Some ships came through accidents like this but in many cases the keel (essentially the spine of the ship) broke. A ship with a broken keel was damaged beyond repair. The crew’s only recourse was to load supplies into smaller boats and try to get home some other way, or to move supplies to the nearest shore, assuming an island or mainland was nearby.
Another method was to lighten the ship. Cannons could be thrown overboard (each cannon might weigh as much as several tons) or heavy cargo could be pitched over the side or if the crew was lucky, hauled to a nearby shore. If the crew was desperate, even the precious drinking water might be pumped over the side.
These actions might allow the ship to float free on the next high tide.
Other actions taken to free s ship that had run aground included running a line to another ship, or even a small boat, and attempting to tow the larger sailing ship clear. Obviously efforts would also be made to harness the wind to drive the vessel off the ground. Once again, if some other kind of solid matter – an island perhaps – was close enough, rope might be tied to anything handy, such a spike run into rock or perhaps a palm tree, in an effort to haul the ship free.
If the vessel was stuck in mud, it might have an un-damaged hull and yet be held firm by suction. In order to break the tension of the mud, the crew might try moving suddenly form one side of the ship to the other, trying to cause enough side-to-side movement that the suction would break. War ships sometimes fired their guns into a muddy entrapment, hoping the shock and vibration would set them free.
These were the good ways to run aground.
The worst way was to be blown onto a rocky shore by storm winds. This was every sailor’s nightmare. On a dark night or in an unfamiliar place, the grounding might come without warning. The momentum of the ship would put a terrible strain on the masts, and it was very common for them to break.
The loss of masts and therefor sails, meant that the ship lost all headway. This put it at the mercy of the sea. With no forward momentum, the ship would turn broadside to the waves. And if the seas were high, waves could wash up over the deck. A strong enough sea might even roll a ship upside down.
This was the disaster that sunk the mighty pirate ship Whydah, flipping her upside down and killing all but 7 of her 150 man crew. It destroyed the Spanish Treasure Fleet of 1715, wiping out 11 out of 12 vessels and strewing gold over Florida’s coasts, and dropping so many doubloons into the sea that they are still washing ashore today.
So, if you go sailing, thank your lucky stars that we now have accurate maps not only of the coasts but of the sea’s bottom as well. And thank them again for boat motors and GPS. Sailing is safer now, though less romantic.