Some people believe that gravity doesn't exist

[The Grand Nudger]

That's nice..and we still don't say that a box has changed it's shape depending on whether or not it's full, so?

[notimportant1234]

-and yet it's shape hasn't changed.  So it must be something else that accounts for the new behavior.  I wonder if there's a term for that something?  

I believe the term you are looking for is, 'dislocating'.

Maybe my spelling isn't as good as yours. But that doesn't mean that I'm wrong about a subject.

[Anomalocaris]

That's nice..and we still don't say that a box has changed it's shape depending on whether or not it's full, so?

A box has changed the amount of air it displaced depending on whether it is full or not.

[The Grand Nudger]

There is really zero fundamental difference between the two description.  They are identical in all effects.   But we are taught to think in terms of one description because that is perceived to be easier to grasp by text book writers.  

That's hardly the reason, lol.  The reason we use the non-novel description is because the sub has not, in fact, changed it's shape. 

But that does not make it truer, or at a fundamental level even any different from the other description.

It's fundamentally truer to the fact that the sub hasn't changed it's shape, simply increased it's mass and therefore overcome the hulls displacement. No different than throwing bricks in a boat till it goes under. Some of the first attempts at subs did use external, detachable ballast. Those subs could more accurately be described as changing their shape..though they didn't do it to submerge..but to surface.

[Anomalocaris]

There is really zero fundamental difference between the two description.  They are identical in all effects.   But we are taught to think in terms of one description because that is perceived to be easier to grasp by text book writers.  

That's hardly the reason, lol.  The reason we use the non-novel description is because the sub has not, in fact, changed it's shape. 

But that does not make it truer, or at a fundamental level even any different from the other description.

It's fundamentally truer to the fact that the sub hasn't changed it's shape, simply increased it;s mass and therefore overcome it's displacement.

That depends on how your perceive shape. If your perception of shape is largely informed by photographs of the outside of the sub, then perhaps it is natural to perceive the shape as having not changed. If you perceive shape as the geometry of that part of the submarine from which water is excluded, then the shape has manifestly changed.

[Gawdzilla Sama]

Not really, because the buoyancy tanks are closed off from the outside. The water in the tanks is the same as the equipment or the crew when it comes to buoyancy.

The buoyancy tank no longer displace water.  It accommodate water now.

You get the concept wrong. The displacement is the hull, not things inside it. The tanks weigh one figure empty and another full, but they don't a change the volume of the submarine by going from one to the other.

---

That depends on how your perceive shape.  If your perception of shape is largely informed by photographs of the outside of the sub, then perhaps it is natural to perceive the shape as having not changed.   If you perceive shape as the geometry of that part of the submarine from which water is excluded, then the shape has manifestly changed.

Submariners perceive shape in a fashion where they don't die on the bottom.

[Succubus]

That depends on how your perceive shape.  If your perception of shape is largely informed by photographs of the outside of the sub, then perhaps it is natural to perceive the shape as having not changed.   If you perceive shape as the geometry of that part of the submarine from which water is excluded, then the shape has manifestly changed.

What you are describing here is a Tardis.

[Anomalocaris]

The buoyancy tank no longer displace water.  It accommodate water now.

You get the concept wrong. The displacement is the hull, not things inside it. The tanks weigh one figure empty and another full, but they don't a change the volume of the submarine by going from one to the other.

---

What you describe is not a concept. It is a convention.

[Gawdzilla Sama]

You get the concept wrong. The displacement is the hull, not things inside it. The tanks weigh one figure empty and another full, but they don't a change the volume of the submarine by going from one to the other.

---

What you describe is not a concept.  It is a convention.

What I described there is the core content of the Navy's professional learning course on ships' buoyancy and stability. I propose that the USN knows more about the topic than you do.

[notimportant1234]

The Navys courses need to be simple because seaferrers need to know a lot of thins before they can navigate.