if something sinks, does it sink indefinitely, or is there a point where water pressure suspends it?
In: Physics
As an object sinks, the water around it gets slightly more dense. If water is squishier than the object, then it will reach a point where it floats neutral. If it is squishier than water, then as it will get denser with water pressure and sink faster as it goes down.
Steel is less squishy than water, but so much more dense that it will never float anyways. A steel container full of air could, under the right conditions, find this neutral buoyancy spot.
There was a famous section in one Terry Pratchett novel where he imagined sunken ships floating in a layer of denser water in the depths of the sea. Now, nobody knows how water works on Diskworld, but in our “roundworld”, water is pretty much not compressible, i.e. it (almost) doesn’t get denser under pressure and therefore this won’t work. At least not in the scales of water depth that we have on Earth.
Pressure wouldn’t suspend it.
Instead, the object would sink until it encounters a fluid that is denser than that object, at which point it could be suspended by buoyancy (i.e. it would float on top of the denser fluids).
This broadly doesn’t happen in Earth’s oceans because water is functionally incompressible, and thus the density of the water wouldn’t really change as you get deeper (e.g. at the bottom of the Mariana Trench, sea water is only about 5% more dense than at sea level). You could do it with an object just *barely* more dense than water (at sea level). Alternatively, you could do it above a brine pool on the ocean floor, with an object denser than water but less dense than the brine (which is about 25% more dense than normal seawater).
You also would get this effect in other fluids that are more compressible (e.g. gases).
Possibly but almost never in practice.
Water becomes very slightly more dense as pressure increases. But the change is very small. Only 2-4% more dense at the bottom of the sea compared to surface.
So if your sinking object is only 2% more dense than surface water then it would stop sinking before reaching ocean bottom. Anything more dense than that would keep sinking.
Also the water pressure may squeeze the sinking item so it may itself become more dense as it sinks.
In water, the Earth’s oceans or lakes? It’s totally dependent on the object and its neutral buoyancy, which is the point where the objects average density is equal to the density of the fluid in which it is immersed.
An iron ship full of water is going to sink to the bottom. Even wooden boats sink, because although wood floats they carry materials like ballast and cargo that brings their average density to a point greater than water.
A creature or an objects neutral buoyancy point can be a point where it floats somewhere in the water column. Fish & other critters do this all the time, raise & lower their buoyancy to move vertically through the water.
Yes absolutely they will stop sinking depending on density. You can but a themometer that demonstrates this very well
https://en.wikipedia.org/wiki/Galileo_thermometer
I’m not sure why people are saying it wouldn’t float. What you are describing is called neutral buoyancy.
This is where the mass of water being displaced is equal to the mass that is displacing it, when both have the same volume. Probably the most commonly seen example would be SCUBA divers adjusting their buoyancy to control their depth.
It’s a hard balance to get right, but not improbable that it will happen by chance either.
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