IT IS ONLY A MOVIE - AND A DUMB ONE AT THAT!
FACT: The destroyer's forward battery would have blown the sub to pieces long before they got within 1000 yards of each other. In this movie, the Japanese gunners were the world’s worst shots ever.
As far as the down the throat shot is concerned, my math says it’s not possible, considering the sub starts fully surfaced, then dives to PD and levels off before firing, with only 1000 yards of space.
Given:
A surfaced Gato class sub could do 21 knots
A Fubuki class destroyer could do 35 knots.
A mid-war Gato took 35 seconds to reach periscope depth
The sub begins it’s descent to PD when the two are 1000 yards apart.
Assumptions:
The sub’s speed never changes during the dive (impossible) rather than switching to batteries, which would reduce maximum speed to 9 knots.
The torpedoes were ready for firing in all respects, including opening the outer doors and flooding the tube (highly unlikely while running surfaced at high speed unless a surface firing was planned – which it wasn’t in this scenario).
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So, we have two objects 1000 yards apart, traveling directly towards each other at a combined speed of 56 knots. The sub starts its dive to PD at this point.
21 knots = 23 mph = 33.7 feet per second
35 secs to PD = 1,181 feet covered by the sub
35 knots = 38.5 mph = 56.5 feet per second
35 secs = 1,976 feet covered by the DD
1181 + 1976 = 3,157 total feet of forward progress
1000 yds = 3000 feet
The DD would have been on top of the sub before it reached PD, let alone had time to fire a torpedo. We won't even discuss the minimum distance the torpedo has to travel before it arms.
Depth charges in the water! GAME OVER ! Nippon wins.
