Sea Mines: The Story of Underwater UXO
Sea mines have shaped naval warfare for centuries, evolving from crude explosives to sophisticated underwater weapons. While these devices were once used to secure coastlines and disrupt enemy fleets, they now represent a lingering threat. Thousands of unexploded sea mines remain scattered across the world’s oceans, posing ongoing risks to maritime safety, marine ecosystems, and coastal communities.
At Brimstone UXO, we are committed to identifying and clearing these dangerous remnants of conflict. Using advanced technology and the expertise of our Navy-trained dive team, we help safeguard marine projects and reduce the risks associated with underwater UXO.
The history of sea mines: from ancient tactics to modern warfare
The origins of sea mines stretch back to 14th-century China, where they were used to defend against pirates. These early devices were rudimentary, often consisting of floating containers filled with gunpowder and ignited by slow-burning fuses.
Over time, sea mines became more sophisticated. During the American Civil War, the Confederate Navy deployed “torpedoes” (as mines were then called) in rivers and coastal waters. These devices were responsible for sinking or damaging dozens of Union ships, marking a turning point in naval combat.
By World War I, sea mines were deployed on a massive scale. The North Sea Mine Barrage, laid by the Allied forces, stretched over 230 miles and contained more than 70,000 mines, designed to hinder German U-boat movements.
In World War II, sea mines played a critical role in both offensive and defensive strategies. The United States’ Operation Starvation used mines to block Japanese shipping routes, crippling the country’s logistics. Meanwhile, Germany’s extensive mining of the English Channel made it perilous for Allied vessels.
The Vietnam War and subsequent conflicts saw the introduction of more advanced mines, equipped with magnetic, acoustic, and pressure-sensitive triggers, making them harder to detect and clear.

The lingering threat: UXO in the world’s oceans
Despite the passage of time, unexploded sea mines (UXO) continue to pose significant risks. Many of these devices remain armed, even decades after being deployed. Some mines have drifted from their original positions, while others have become buried under sediment, making them difficult to locate.
Sea mines can still cause catastrophic damage, including:
- Threatening maritime activities: UXO can endanger commercial shipping, fishing operations, and offshore energy projects.
- Risking coastal safety: Mines that wash ashore pose a hazard to beachgoers and coastal communities.
- Harming marine ecosystems: Underwater detonations can devastate local wildlife and coral reefs.
Types of sea mines: understanding the danger
Sea mines come in various forms, each with distinct placement and triggering mechanisms. These include:
Bottom Mines:
- Rest on the seabed, typically in shallow waters.
- Triggered by the magnetic or acoustic signature of passing ships.
- Harder to detect due to their low profile.
Moored Mines:
- Suspended at varying depths, anchored by a chain or cable.
- Designed to strike the hull of passing vessels.
- Over time, corrosion or strong currents can cause them to break free and drift, making them unpredictable.
Drifting Mines:
- Float freely on the water’s surface.
- Detonate on contact with ships or other objects.
- Outlawed by the Hague Convention of 1907 due to their indiscriminate nature, but some still exist in the world’s oceans.
Influence Mines:
- Modern mines that use magnetic, acoustic, or pressure-sensitive triggers.
- Can differentiate between military and civilian vessels, reducing the risk of collateral damage.
Limpet Mines:
- Manually attached to the hulls of ships by divers.
- Used in sabotage operations rather than large-scale mining.
Clearing sea mines: Brimstone’s marine UXO expertise
At Brimstone UXO, we provide comprehensive marine UXO detection and clearance services, ensuring your offshore projects are safe from the risks of unexploded sea mines. Our specialist approach includes:
Advanced Survey Technology:
- We use multibeam sonar and magnetometry to create detailed seabed images, allowing us to detect and map ferrous (metallic) objects that could be UXO.
- This technology enables us to locate mines buried under sediment or partially hidden by underwater terrain.
Expert Dive Teams:
- Our Navy-trained dive team has over 200 years of collective diving experience, ensuring precision and safety during underwater operations.
- Each project is supervised by diver medic technicians and overseen by former Royal Navy clearance divers, guaranteeing the highest standards of safety and professionalism.
Safe and Efficient Clearance:
- Once UXO is detected, we follow strict safety protocols to remove or dispose of the threat.
- Our teams work swiftly to minimise project delays while prioritising safety and environmental protection.

The importance of marine UXO clearance
For maritime construction, offshore wind farms, and port expansions, thorough UXO clearance is critical. Failing to address the risks of sea mines can lead to:
- Project delays due to unexpected UXO discoveries.
- Financial losses from damage, legal claims, or downtime.
- Endangerment of personnel working in affected areas.
By partnering with Brimstone, you benefit from efficient and reliable UXO risk mitigation, allowing your projects to proceed without disruption.
Protect your marine projects with Brimstone UXO
The threat of sea mines may be rooted in history, but their risks are very much a modern reality. Through expert intervention, cutting-edge technology, and a commitment to safety, Brimstone UXO is at the forefront of marine UXO clearance.
If you require UXO risk assessments, marine surveys, or clearance services, get in touch with us today. Our team is ready to help you navigate the complexities of marine UXO and ensure the safety of your project.
Contact us by filling out a form on our website.
Stay connected by following us on Facebook, Instagram, Twitter, LinkedIn and YouTube.
"*" indicates required fields