# Why weren't there reverse depth charges?

**URL:** <https://boards.straightdope.com/t/why-werent-there-reverse-depth-charges/716857>\
**Category:** Factual Questions\
**Created:** [April 5, 2015, 3:45am UTC](https://boards.straightdope.com/t/why-werent-there-reverse-depth-charges/716857 "2015-04-05T03:45:18Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\
**Post date:** [April 6, 2015, 7:38pm UTC](https://boards.straightdope.com/t/why-werent-there-reverse-depth-charges/716857/21 "2015-04-06T19:38:01Z")

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> [@Malthus](#):
>
> Subs were commerce-destroyers during WW2. Their job was typically to sink merchant shipping, not to take on warships mano-a-mano.
> 
> Certainly it happened that subs sank warships, but that was not what they were for: and a sub that made it a habit was likely to end up a dead sub.

This is true except for the Japanese, who saw theirsubs as, basically just another form of warship. Their subs were by far the least effective of the major power.

On second thought, I should probably take that last bit back. I was referring to Germany, the US and Japan, and there were several other countries using them but I don’t know much about their policies, success rate, etc. Italy, Russia, and England all used subs, and maybe some more too.

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**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\
**Post date:** [April 7, 2015, 1:35am UTC](https://boards.straightdope.com/t/why-werent-there-reverse-depth-charges/716857/22 "2015-04-07T01:35:12Z")

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> [@Kobal2](#):
>
> They often did surface attacks at night actually. WW2 submarines had abysmal underwater performance - crap speed, crap acceleration, crap endurance… To give you an idea, a Type VII U-boot could do 7, maybe 9 knots submerged. Your average freight liner tooled around at 15. A warship could cruise in the high 30s. So unless the submarine had both a hell of a head start and/or advanced knowledge of their target’s course and speed, thus be able to race ahead and lie in wait, they had to chase on the surface and trust in their low visibility to remain unnoticed.  
> WW2 subs really have to be understood as “surface boat that can submerge”, not “underwater boat that could conceivably come up” like modern subs are.

While this is an accurate description overall, I will nitpick your speeds – they’re a little too high. Wikipedia puts the max submerged speed of a Type VII U-boat at 7.6 kts, and fast convoys at 9-13 kts, slow convoys at 8 kts. 15-knot ships generally sailed independently and were considered very fast. They existed, but I wouldn’t call them average.

Otherwise you’re dead on.

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