Question for the surface/ASW Navy types

[MillCreek]

I am reading an article in today's WSJ about the Baltic states ramping up military spending to counter Russia.  The line below was in the article.

Finland’s navy on Tuesday dropped small depth charges to warn off a suspected submarine detected near Helsinki.

I suspect these 'small depth charges' were essentially noisemakers, and not the classic ash cans of WWII.  So what would be used for this purpose?  Is there a specific device for this sort of thing, or is someone chucking hand grenades over the side?

[BobR]

We used to carry little explosive signaling devices that acted like a tiny depth charge I suppose. They looked like little mortar rounds and had a couple of different depth settings on them. If we taped 4 of them together we could still get them out of our free fall chute, and it made a bigger bang. We would use them when doing exercises with friendly subs to let them know we had localized them and dropped a torp or depth bomb on them.

We would also do occasional flights from Adak to Hawaii dropping one at preset intervals for calibration of stuff.

I imagine this is something along the lines of what they are dropping. Just something to tell the sub "We know you are here and you need to leave, thank you".

Personally I think they should drag a line until they snag it and then send noisemakers down the line to slap against the hull for a while.

bob

[RoadKingLarry]

Problem with dragging a line and snagging a sub would be what to do once you catch one. A line stout enough to do any good might endanger the surface vessel.
On the other hand trawl lengths of cables on light line and get some of that caught on the subs screw and they likely have to surface .

[MechAg94]

Why use noisemakers?  Just drop some real depth charges where you are pretty sure the sub isn't.  Good training I would think.

[AJ Dual]

Why the Vatican has a sub fleet in the first place is beyond me...

[TommyGunn]

A man I used to work for shortly after graduating college had been a US Navy vet.  He once told me about serving aboard a destroyer in the Caribbean.  The water was so clear in places they would spot a soviet sub, but they could also see it from the deck, lurking below.   
They'd get a bunch of fragmentation grenades, wrap up the spoon with a few winds of toilet paper, pull the pin, and toss them overboard where if they'd guessed how much tp to use, it would degenerate enough to pop the spoon off at the right depth and the grenade would then go off.
It didn't do much more than knock off some flakes of paint off the sub....except maybe to the hydrophone operator's eardrums ..... .... but it did cause some of them to change course ....

[birdman]

A man I used to work for shortly after graduating college had been a US Navy vet.  He once told me about serving aboard a destroyer in the Caribbean.  The water was so clear in places they would spot a soviet sub, but they could also see it from the deck, lurking below.   
They'd get a bunch of fragmentation grenades, wrap up the spoon with a few winds of toilet paper, pull the pin, and toss them overboard where if they'd guessed how much tp to use, it would degenerate enough to pop the spoon off at the right depth and the grenade would then go off.
It didn't do much more than knock off some flakes of paint off the sub....except maybe to the hydrophone operator's eardrums ..... .... but it did cause some of them to change course ....

A visual sighting through unusually clear water is pretty much a recurring nightmare for bubbleheads.