BLOCKER.

This is coolbert:

Finland has them! Estonia does also?

Naval sea mines the cost effectiveness of this naval warfare weapon cannot be exaggerated.

From CORPORAL FRISK and than thanks to same.

"My Mines and those of My Brother"

"Naval mines have a tendency to stay largely out of sight, until they suddenly pop up to remind everyone about their existence. This goes both for the weapons themselves, as for their role in the grand scheme of things. The Baltic Sea, always a favorable battlefield for mines, has seen a number of interesting development during the last few weeks"

From 1917 and the era of the Great War as planned naval mines a rather insignificant number able to control the entrance/exit to the Gulf of Finland or the Gulf or Riga. Baltic Sea.

Same area Gulf or Finland and Gulf of Riga showing geographic context.

These Finnish sea mines evidently of the BLOCKER variety:

"BLOCKER

A MODERN COST-EFFECTIVE INFLUENCE MINE

'influence mine [′in‚flü·əns ‚mīn]

(ordnance)

A mine that is detonated by methods that are different than target contact.'

Modern Influence Mine with devastating performance. Cost-effective system with long shelf life and minimal maintenance during the life cycle. Acoustic-, pressure- and magnetic sensors. Optional underwater electrical potential sensors. NEQ equivalent to over 1000 kg [2,000 pounds] of TNT."

See the various prior blog entries the efficacy of naval sea mines unquestioned:

https://militaryanalysis.blogspot.com/2021/04/dolphin.html

https://militaryanalysis.blogspot.com/2020/04/port-arthur.html

https://militaryanalysis.blogspot.com/2020/03/barrage.html

coolbert.