Hi Zach!

Since a surface vessel depth charging a Uboat,had to pass over
its planned victim,and roll off the depth charges from the ship´s stern,
the attacking surface vessel always lost asdic contact with the Uboat,
during the last few hundred yards,of its attack run.

This was solved by A/S vessels being equipped with the Hedgehog:
An ahead throwing weapon wich fired of a number of explosive projectiles,
wich landed far ahead of the attacking vessel,
while the A/S vessel still was in asdic contact with its supposed victim.
These Hedgehog projectiles exploded only on direct contact with the Uboat however!!
And was therefore depending on a direct hit,so to speak.
Another bad thing about the Hedgehog was that the weapon
had a very heavy recoil,and hence could only be used by heavier A/S vessels.

In 1945 the Royal Navy had developed a new weapon called SQUID:

The Squid; instead of depending on a direct contact hit with the Uboat;,
fired 3 large Depth Bombs ahead of the ship,
set at a depth predicted by the asdic!!,
and hence these proved highly effective.

Best regards/Anders.