DSEI UK 2025: Forcit Defence presents sea mines for the first time

Forcit Defence has been a long-time provider of area denial weapons to the Finnish Defence Forces, and has now made its suite of sea mines available for export with two of the capabilities on display during DSEI 2025. 

The company has two primary sea mine capabilities; Blocker, a large mine with an explosive yield equivalent to 1,000 kg of TNT, and a newer system called Flounder, which is designed as an anti-invasion coastal mine, according to the company’s literature. 

A Forcit Defence representative explained that they have provided sea mines for over a decade, but with Finland recently joining NATO and the demand for area denial capabilities growing, they have been granted permission to export them. 

Flounder includes a new generation of sensor system, which enables navies to develop their own detection and detonation algorithms. This is achieved through the Target Detection System from Forcit, which is fitted to both mines and can be retrofitted to older mines, improving their performance. The Blocker mine has acoustic, pressure, magnetic, and inertial sensors and can optionally be fitted with UEP (Underwater Electric Potential) and photonic sensors, according to the company’s brochure.  

Blocker is already in service and can be deployed using the Cube Sea Mine Laying system from SH Defence, which was also present at DSEI. The Cube is based on the standard ISO container and available in both 20 and 40-foot configurations. The Cube can be semi- or fully-automatic, allowing a single crew member to operate it. And it can be fitted to a boat in a matter of minutes using a crane, and then swapped for other modules, which include uncrewed sub-surface vessel configurations, weapons systems, and a variety of other configurations. According to SH Defence, this allows even small off-shore patrol vessels to be turned into minelayers without significantly altering anything else on the ship. 

Technical explainer: UEP

An Underwater Electric Potential sensor is a specialised device used in a naval and military context to detect the electrical signature of ships, submarines, and other vessels. This is primarily caused by corrosion and corrosion-resistant paints on the hull of a ship. A UEP sensor can be programmed only to detonate the mine when a selected electrical signature is detected. 

Calibre comment

Area denial weapons are growing in importance on land, and Forcit Defence has already provided its Sentry anti-tank capability to Lithuania. It is integrated into the country’s plans for a layered defence from the border. They are also as important at sea as NATO navies have shrunk in numbers of surface vessels and crews. Sea mines can help to channel enemy ships or limit their freedom of operation, helping to make tracking them more manageable. 

By Sam Cranny-Evans, published on September 11, 2025. Credit for the lead image is Calibre Defence. The bottom left image shows the Cube system from the SH Defence website, the remaining three show Flounder and Blocker, taken by Calibre Defence during DSEI UK 2025.