If you are scuba diving, and you swim under a big ship, what would happen?
It was really weird. I come to ask this question because on tv, someone swam under a big ship such as this one: http://www.colorfoundry.com/images/cargo.jpg | and when he got under the ship, he blacked out. Could the pressure, and weight of the ship knocked him out? Since all that weight is going downwards into the water, would that create pressure?
It was as big as a cruise ship, and was stacked 3/4 as high as the worlds biggest one. It was a boat inspection, i’ve never been scuba diving before. But why would that not do anything to him, does the boat just sit there, being a weight-less boey?
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Tags: diving, happen, scuba, Ship, Swim, UNDER, Would
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Not that much pressure, he must be a weakling girly man.
Nope. It had nothing to do with the vessel if it didn’t hit the diver. There is no pressure applied by the ship on the diver at all. There is additional pressure applied to the diver every foot he or she descends, yes, but it has nothing to do with the ship. The mass of the ship is exactly the same as the mass of the volume the ship displaces. In other words…it’s like that ship isn’t there. That hole in the water is the same mass of that volume of water as if that ship weren’t there.
Yes, the vessel is sitting there buoyant. It’s total mass is equal to the amount of mass of the volume of water it’s hull displaces.
The diver in your example either was hit by a moving vessel, suffered some sort of medical issue , had a problem with using the wrong gas mix for the depth he’s in or had some sort of regulator failure he couldn’t deal with. Not many vessels draw more than 30 feet so it wasn’t a case of diving too deep.
I’ve had a 600 foot cargo vessel in the St Lawrence seaway thunder overhead while I was diving a wreck and been under a stationary icebreaker. Neither caused any difference in pressure other than the wall of sound that hit me from the cargo vessel and a bit of wash from the prop and wake.
Was this TV show fictional or a real event? If it was a real event I would suspect there is more to the story than simply swimming under the ship that led to the diver losing consciousness. If it was fictional…well, many things done in TV shows or in the movies don’t match reality.
To address your specific question about pressure, I don’t think swimming beneath a submerged object would result in any change in pressure. Pressure is a measurement of force exerted uniformly over a surface area. As it applies to scuba divers, this force is the force of gravity acting on the earth’s atmosphere as well as the water above us which gives weight to both the atmosphere and the water. This weight acts upon the surface of our bodies to exert pressure.
When a ship (or object of any kind) floats, it displaces (moves out of the way) a volume of water equal to its weight on land. This volume of displaced water is less than the total volume of the ship, and so only a portion of the ship is submerged below the surface. Since pressure at depth is directly related to the weight of things above us, there should be no pressure change beneath the ship because the weight of the water displaced by the ship is exactly matched by the weight of the ship itself. Since the net change in weight is zero, the net change in pressure should also be zero.
There are other things that could cause a diver to lose consciousness at depth. Using the wrong oxygen mixture in the breathing gas could result in either too little oxygen at depth or too much, and either case could result in loss of consciousness. Another possibility is that the breathing gas was contaminated with carbon monoxide which at depth reached toxic levels. Or the diver may just have had some medical problem unrelated to being underwater. Without knowing more details about the the depth the diver was at, the kind of equipment he was using, and the type of gas he was breathing all one can do is make guesses.
I do feel pretty confident, though, that the ship itself causing a change in pressure was not a factor.