“The Poseidon Adventure” was a 1972 movie about a cruse ship that gets capsized by a giant wave and is left floating upsidedown with the bow underwater and just the rear of the ship with the propellers left floating above water.
The story is about a small group of survivers trapped inside the upsidedown ship trying to find a way out. They decide to make their way to rear of the ship, which is the only part still above water and into the engine room where the steel hull is thinnest so possibility of an easier rescue.
OK a good story and they have plenty of hazards and obstacles to overcome before they get to the engine room and bang on the bottom of the hull and get rescued.
But would this even be possible? The whole ship is being kept afloat by the air pocket in the stern where the survivers are trapped. Surely the air pressure in there would be tremendous, could people survive such pressure?
Then when they are saved by the rescuers cutting a hole in the hull wouldn’t the rush of escaping air have been dangerous for those outside as well as those inside the hull and surely now with the air gone the ship would sink within moments.
I know it’s only a Hollywood movie but filmmakers usually try to keep storyline’s within the realms of possibility, but unless I’m missing something obvious this ending does not seem at all feasible.
If there’s enough air in there to keep the hull from sinking, then almost by definition, it wouldn’t be under great pressure (because air under pressure shrinks to a smaller volume, which displaces less water, which allows the hull to sink).
It’s going to be greater than ambient pressure, because of the weight of the submerged hull, but it’s not going to be as high pressure as a traditional open-bottom diving bell at depth.
Generally, ships are divided into compartments, and the air would only escape from the compartment that is opened - so there might be sufficient air in other compartments to prevent sinking (or maybe not, in a real-life situation)
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I saw the movie in the company of a welder, and he pshawed the ending for the reason given in the OP.
But this subject has come up enough times, here and on other fora, that the argument from compartmentalization is convincing. The buoyancy would probably be sealed off by bulkheads, and so cutting through the hull is not necessarily as stupid as my welder friend thought.
The little bit of the story that I saw was so unbelievable that I did not watch but just a few moments here and there.
Ship rolls over boiler explodes water from the condenser hits the spinning turbine blades and it comes apart. That means that you no longer have any lights. Emergency generator oops the diesel engine is not meant to run upside down so no emergency power. And emergency battery pack lights at best are good for only 45 minutes.
So any parts with lights on is unbelievable. The same anytime they show power sparking from live electrical busses.
As for the ending. Ships built at that time had double bottom tanks. So if they were pounding on the bottom of the engine room they were pounding on the top of the double bottom tanks. So if they could hear the pounding, they would first have to cut through skin of the ship. Remove the oil or water from the tank. Then cut through the tank top. Assume the depth of the water is 50 feet. That is a pressure around 25psi above atmosphere . Cutting through the metal with that pressure on one side would be difficult. And if they were in the engine room that space would rapidly fill with water and I doubt the ship would stay up.
<I know it’s only a Hollywood movie but filmmakers usually try to keep storyline’s within the realms of possibility, but unless I’m missing something obvious this ending does not seem at all feasible.>
From what I saw of this movie it was a possible as some of the cartoons that kids watch.
To nitpick myself also - air would only escape from the opened compartment if water could enter it to displace the air. If (for example) you move into an air-filled compartment and seal the door behind you, then someone cuts a hole in the skin of the compartment you are in, there will be no net loss of air or buoyancy (assuming the hole they cut is above the waterline).
It’s been a few decades since I saw it, but I did watch it several times back then, and I don’t recall even once, any of the characters saying anything remotely similar to, “Remember to shut that door so the ship is sectioned off and we don’t lose our air!”
I don’t remember everything 100%, but the story in the book is a bit different. (The book came first, before the movie). I seem to remember in the book that as the passengers were being taken off, the ship began to make noises that indicated it was sinking, and it did finally go under in view of the survivors soon after they got off.
The Poseidon was supposed to be (in the early 1970s) a decades-old liner that was on its last voyage before going to the scrapyard. It might have been built in the 1930s- does that change anything?
But weren’t they in the engine room. Water tight doors are only under the water line. The top of the engine room would be above the water line. There are intake and exhaust air vents, the stack, the doors into the engine room and many more places for water to enter.
Titanic sank in only 3 hours from first hole to going under. The Poseidon had been filling with water for many more hours so would have had a lot of water in it to begin with. The “tiny” hole would have been at least 14 inches of diameter. A lot of air can escape through that size of hole in minutes.
The inverted ship is open at the bottom. The air pressure in the air pocket will be the same as the water pressure at the depth where the surface of water in the ship is. I.e. if the water inside the inverted ship comes up to 30 ft below the water surface outside, then the pressure in the air pocket is the same as water pressure at 30 ft depth. (The water surface inside must be lower than outside, otherwise the air can’t provide any buoyancy.)
The effect on a person would be the same as diving to that depth using scuba gear. Pressure itself won’t do any harm, but rapid decompression could cause a problem (decompression sickness, or bends) when the rescuers cut open a hole and suddenly equalize the pressure.
I agree that if the survivors could seal themselves in a watertight and airtight compartment, cutting a hole into the hull in that compartment won’t cause the ship to sink any further. And if they first drilled a small hole and let the pressure equalize slowly, they could avoid decompression sickness.
Note on air pressure: if the water level inside the upside-down hull is at the same level as the ocean, the air pressure inside is about the same as on the outside. In the movie, the water level is a bit lower inside than out (and rising) so it wouldn’t be all that high.
IIRC, while the hull was being cut open, etc., the survivors could see the water coming up thru a hatchway. (I can’t find a YouTube clip for this.) Once the hull was breached, there should have been a rush of air out the hole. Depending on the buoyancy of the other compartments, this might continue thru the rescue.
Are we assuming the sequel is non-canon here? In that movie, the ship was still floating for some time after the end of the first movie, complete with other survivors that Michael Caine encounters in searching for the fortune.
Of course, while the bends might be very painful and damaging, it’s still survivable. If it’s a choice between getting the passengers out quickly and giving them the bends, or getting them out so slowly that the ship finishes sinking and they drown, you choose the bends.
