Speed became an enemy after the torpedoes hit
A damaged ship moving through water experiences forces a stationary ship does not.
Water presses against ruptured plating.
Movement can increase inflow through damaged sections.
Internal flooding can therefore worsen more rapidly while the ship maintains speed.
This appears to have happened aboard Shinano.
The outer hull had been opened.
Water entered damaged starboard compartments.
Instead of stopping at intact internal boundaries, it found unsealed passages.
The ship's continued movement helped feed the flooding.
The list increased.
Abe eventually reduced speed, but precious time had passed.
The carrier had moved many miles after being hit, demonstrating how long her propulsion survived while simultaneously worsening the flooding problem.
This is another reason the sinking can appear mysterious.
A ship that continues steaming for hours seems healthy enough to save.
Propulsion is only one measure of survivability.
Shinano's engines could still move the hull while the hull's reserve buoyancy was disappearing.
The machinery was winning one battle.
The sea was winning another.
Counter-flooding temporarily hid the seriousness of the problem
When a ship takes major flooding on one side, it develops a list toward the damaged side.
A severe list can become dangerous for several reasons.
Openings normally above the waterline can become submerged.
Pumps may function poorly.
Machinery can lose lubrication or feedwater arrangements.
Crew movement becomes difficult.
Eventually the ship can capsize.
One response is counter-flooding.
Compartments on the opposite side are intentionally filled with seawater.
This adds weight where it is needed to reduce the list.
The technique can be effective.
It also comes with a cost.
Every ton of seawater deliberately admitted is another ton the ship must carry.
Counter-flooding corrects balance by sacrificing reserve buoyancy.
It does not remove the original floodwater.
A ship using counter-flooding therefore needs the original flooding to be controlled.
Shinano's was not.
Abe ordered flooding of spaces on the port side, including boiler rooms, to compensate for the starboard list. U.S. Navy historical accounts note that three outboard port boiler rooms were intentionally flooded.
The measure helped temporarily.
The ship became more upright.
That improvement could create false reassurance.
The visible symptom had been reduced.
The underlying water intake had not.
Progressive flooding continued.
The ship was now carrying both uncontrolled water on the starboard side and deliberate floodwater on the port side.
The reserve that might have supported survival was shrinking from both directions.
Shinano's size became a disadvantage during towing
A ship of Shinano's displacement contains enormous inertia.
That helps provide stability in normal conditions.
It becomes difficult when the ship loses propulsion.
By dawn, the flooding had damaged the carrier's ability to operate machinery. U.S. Navy accounts state that boiler feedwater problems eventually left Shinano dead in the water after she had traveled roughly 36 miles from the point of attack.
Once propulsion stopped, the situation changed again.
The carrier could no longer steer effectively toward shallow water or a protected anchorage.
Escort destroyers attempted to tow her.
The effort was inadequate.
A destroyer is powerful for its size, but Shinano weighed tens of thousands of tons and was already listing while carrying massive amounts of floodwater.
The tow lines could not easily move such a hull through the sea.
Even if towing had succeeded, the carrier still needed to remain afloat long enough to reach safety.
Progressive flooding continued while the tow attempts consumed time.
Shinano had become an enormous passive object.
Her size, which had seemed like strength, now made her almost impossible for the escorts to control.
The sequence from torpedo attack to sinking lasted nearly eight hours
The carrier did not vanish minutes after Archerfish fired.
This is important because it shows the torpedoes were not equivalent to an instant fatal explosion.
They created a condition that worsened over time.
The attack occurred shortly after 3:00 a.m.
For hours afterward, Japanese personnel attempted to control flooding.
The ship continued moving.
Counter-flooding was attempted.
Machinery failed gradually.
Tow attempts followed.
At 10:18 a.m., Captain Abe finally ordered the ship abandoned.
Approximately 40 minutes later, around 10:57, Shinano rolled over and sank by the stern.
That timeline is the strongest evidence for the real cause.
If the torpedoes had simply shattered an inherently weak hull, Shinano would likely have gone down quickly.
Instead, the ship survived long enough for damage-control quality to determine the outcome.
Her fate was decided in those hours.
Every open penetration mattered.
Every missing pump mattered.
Every inexperienced sailor mattered.
Every delay in recognizing the seriousness mattered.