Komatsu D155W: The Underwater Bulldozer That Changed Marine Construction

The World’s First Amphibious Bulldozer

Since its introduction in 1971, the Komatsu D155W has remained one of the most remarkable and unconventional pieces of heavy machinery ever built. Designed to operate entirely underwater, this 95,000-pound amphibious bulldozer was engineered for underwater excavation, dredging, and land reclamation projects where traditional equipment could not function. With only 36 units ever produced, and just five still in active service, the D155W is a rare testament to Komatsu’s innovation in the field of marine construction.

The D155W was the world’s first commercially marketed amphibious bulldozer, and its design reflects a blend of heavy equipment engineering and submarine technology. Unlike standard dozers, which are limited by water depth, the D155W can operate at depths of up to 23 feet. Its most distinctive feature is its fully sealed engine compartment, ensuring that all internal components remain protected from water intrusion. The engine itself is a modified version of the 6-cylinder diesel engine found in the Komatsu D155A, producing 302 horsepower at 1,900 RPM.

To function underwater, the D155W utilizes an advanced snorkel system, similar to those used in submarines. This system provides fresh air to the engine while also housing a specialized compressor for additional airflow. The extra-wide tracks—over 2.3 feet in width—provide exceptional stability, allowing the machine to maneuver across underwater terrain with minimal resistance. Due to the limited visibility in submerged environments, the D155W is remotely operated, improving safety and control during underwater operations.

The primary role of the D155W was to assist in underwater dredging, port construction, and land reclamation projects. Most units were deployed across Japan, the Philippines, and Europe, where they played a crucial role in shaping harbors, riverbeds, and coastal infrastructure. Unlike large-scale dredging equipment or long-reach excavators, the D155W offered a more compact and maneuverable alternative for underwater earthmoving, particularly in confined spaces where floating barges or dredging ships were impractical.

One of the most unexpected applications of the D155W was its deployment at Chernobyl following the 1986 nuclear disaster. Due to its remote-control operation, the machine was used to assist in hazardous cleanup efforts in areas where radiation levels were too high for human operators. This adaptability further solidified the D155W’s reputation as one of the most versatile and unique bulldozers ever manufactured.

Despite its groundbreaking design, the D155W never saw widespread production, with only 36 units ever built. The high costs associated with manufacturing, operating, and maintaining such a specialized machine likely limited its appeal, particularly when alternative dredging solutions were available. Nevertheless, Komatsu remains a leader in this niche market, and the few remaining D155W units continue to serve in marine construction projects worldwide.

Today, the D155W stands as a rare example of Komatsu’s dedication to engineering solutions for extreme environments. While other amphibious and underwater construction machines have been developed over the years, the D155W remains one of the most fascinating pieces of heavy equipment ever produced—a true blend of innovation, power, and resilience.

PHOTOS BY DW STAFF