Commercial diving involves a broad range of underwater activities, often requiring specialised equipment to perform tasks efficiently and safely. Among the frequently used equipment in commercial diving are underwater lift bags. These versatile devices are indispensable in various underwater operations, from salvage and recovery to construction and maintenance. This article looks the mechanics of underwater lift bags, their applications, and the types supplied by iSubC.

Understanding Underwater Lift Bags

How They Work

Underwater lift bags function based on the principles of buoyancy. The fundamental concept involves filling a bag with air to provide sufficient buoyant force to lift objects submerged underwater. Here’s a step-by-step overview of their operation:

  1. Attachment: The lift bag is securely attached to the object that needs to be lifted. This is typically achieved using rigging and straps designed to handle the load.
  2. Inflation: Compressed air is introduced into the lift bag, either from scuba cylinders or surface-supplied air. As the bag inflates, it displaces water, creating an upward buoyant force.
  3. Lifting: Once the bag generates enough buoyant force to overcome the weight of the object and any additional resistance (such as mud or silt suction), the object begins to rise.
  4. Controlled Ascent: The ascent must be carefully managed to ensure safety and precision. Divers may adjust the air volume in the lift bag to control the rate of ascent and maintain stability.
  5. Surface Recovery: Upon reaching the surface, the object can be recovered using cranes or other lifting equipment, or it may be towed to a designated location for further handling.

Key Components

  • Lift Bag Fabric: Typically made from durable, reinforced materials such as PVC or nylon, which can withstand the harsh underwater environment and high pressure.
  • Inflation/Deflation Valves: Essential for controlling the air flow into and out of the lift bag, allowing for precise buoyancy adjustments.
  • Straps and Rigging: Used to attach the lift bag securely to the object being lifted. These components must be robust enough to handle the load without failure.

Applications of Underwater Lift Bags

Underwater lift bags are employed in a variety of commercial diving operations, each requiring specific features and capabilities:

1. Salvage Operations

Salvage operations often involve recovering sunken vessels, aircraft, or other heavy objects from the seabed. Lift bags provide the buoyancy needed to raise these objects to the surface, where they can be further managed.

2. Construction and Maintenance

In underwater construction, lift bags are used to position and install heavy structures such as pipelines, subsea infrastructure, and marine habitats. They enable precise placement and alignment, ensuring the stability and integrity of the construction.

3. Marine Research and Exploration

Lift bags assist in retrieving scientific instruments and samples from the ocean floor. They are crucial in marine biology, archaeology, and geology, where delicate handling of artifacts and samples is required.

4. Environmental Remediation

In environmental cleanup projects, lift bags help remove debris, pollutants, and hazardous materials from underwater sites. Their controlled lifting capabilities ensure minimal disturbance to the surrounding environment.

5. Emergency Response and Recovery

Lift bags play a vital role in emergency scenarios, such as recovering vehicles and equipment from water bodies. Their rapid deployment and efficiency make them indispensable in search and rescue operations.

Types of Underwater Lift Bags Supplied by iSubC

iSubC offers a comprehensive range of underwater lift bags tailored to meet diverse operational needs. Below are some of the key types available:

1. Enclosed Flotation Bags

Enclosed flotation bags are designed for lifting and supporting loads in shallow water and surface operations. Their enclosed design ensures a controlled and stable lift, minimising the risk of sudden deflation or loss of buoyancy.


  • Available in various capacities, typically ranging from a few hundred kilograms to several tonnes.
  • Made from high-strength materials for durability.
  • Equipped with multiple inflation/deflation valves for precise control.
  • Ideal for lifting submerged objects to the surface and maintaining buoyancy during towing operations.

2. Salvage Pontoons

Salvage pontoons are large, cylindrical lift bags used in major salvage operations. They provide substantial lifting capacity and are often employed in conjunction with other lifting equipment to raise sunken vessels and heavy objects.


  • High buoyancy capacities, often exceeding several tonnes.
  • Durable construction to withstand the rigors of salvage operations.
  • Multiple attachment points for secure rigging.
  • Can be used individually or in combination for larger lifts.

3. Vehicle Recovery Systems

Vehicle recovery systems are specialised lift bags designed for recovering submerged vehicles, such as cars, trucks, and buses. These systems provide the necessary buoyancy and stability to lift and transport vehicles to the surface safely.


  • Configured to handle the specific shape and weight distribution of vehicles.
  • Reinforced materials and construction for enhanced durability.
  • Equipped with inflation/deflation valves and safety features to ensure a controlled lift.
  • Ideal for use in emergency response and accident recovery operations.

Explore our Lift Bags

Advantages of Using iSubC Underwater Lift Bags

iSubC’s range of underwater lift bags offers several advantages, making them a preferred choice in the commercial diving industry:

1. Quality and Durability

iSubC lift bags are manufactured from high-quality materials, ensuring long-term durability and reliability. Their robust construction allows them to withstand the harsh underwater environment and the demands of heavy lifting.

2. Versatility

With a wide range of lift bags available, iSubC caters to various applications, from salvage and construction to emergency recovery and environmental remediation. This versatility makes their lift bags suitable for diverse operational needs.

3. Precision and Control

The lift bags are equipped with multiple inflation and deflation valves, allowing for precise control over buoyancy. This ensures a controlled and stable lift, minimizing the risk of accidents or damage to the objects being lifted.

4. Ease of Use

iSubC lift bags are designed for ease of use, with user-friendly attachment and detachment mechanisms. This simplifies the deployment and retrieval process, saving valuable time during operations.

5. Safety

Safety is a paramount concern in underwater lifting operations. iSubC lift bags are designed with safety features, including reinforced straps, secure attachment points, and reliable inflation/deflation systems, ensuring safe and efficient lifts.


Underwater lift bags are essential tools in the commercial diving industry, enabling divers to perform a wide range of tasks with precision and efficiency. Whether it’s lifting heavy objects during salvage operations, positioning structures in underwater construction, or recovering vehicles in emergency situations, lift bags provide the necessary buoyancy and control.

iSubC offers a diverse selection of underwater lift bags, including enclosed flotation bags, propeller underwater lift bags, salvage pontoons, and vehicle recovery systems. Each type is designed to meet specific operational requirements, ensuring reliability, durability, and safety in various underwater scenarios.

Contact iSubC today for more information or to request a quote.