How Do Marine Recovery Airbags Work?
Marine recovery airbags provide controlled buoyancy and support for vessels, submerged objects, and other marine assets that need to be lifted, refloated, launched, retrieved, or repositioned. They can be especially useful where conventional lifting access is limited or where a recovery needs to be carried out gradually rather than with a single crane lift.
The basic principle is simple: an air-filled bag displaces water and creates buoyancy. In practice, however, using marine recovery airbags requires careful planning around the weight and condition of the vessel, the position of the load, the water depth, access, inflation sequence, and what needs to happen once the asset begins to move.
For South Australian projects involving vessel recovery or marine lifting, Send It Marine provides marine airbag recovery services and specialised recovery airbags for suitable marine applications.
What is a marine recovery airbag?
A marine recovery airbag is a heavy-duty inflatable device used to create buoyancy, flotation, or rolling support around a vessel or other marine load. Depending on the design and application, the bag may be positioned under a vessel, attached to a submerged object, or used between the asset and the shore to assist movement.
Marine airbags come in different forms. Long cylindrical airbags are commonly used for vessel launching, retrieval, refloating, and shore-based movement. Underwater lift bags are typically shaped differently and are more commonly attached to submerged loads to generate vertical lift.
That distinction matters because the equipment is selected around the job. A long cylindrical airbag supporting a vessel from below performs a different role from a smaller parachute-style lift bag attached to an underwater object, even though both rely on air displacement and buoyancy.
How do marine airbags create buoyancy?
When an airbag is inflated in or near the water, the air inside it creates a volume that displaces water. That displacement produces an upward force. When enough buoyancy is introduced, it can reduce the effective underwater weight of a vessel or object and make it easier to lift, stabilise, or move.
The amount of support required depends on the load. A partially submerged boat may only need additional buoyancy to regain stability, while a heavily flooded vessel may require a much larger recovery setup involving several airbags, pumping, lifting equipment, or a combination of methods.
Buoyancy also needs to be distributed appropriately. If too much lift is introduced at one point, a damaged vessel can shift, rotate, or place additional stress on the hull. Recovery planning therefore considers where the airbags should be positioned and how inflation should be staged.
How are marine recovery airbags positioned?
The positioning method depends on whether the vessel is submerged, stranded, grounded, or being launched or retrieved from shore. The recovery team first needs to assess the vessel's shape, condition, weight distribution, and available access.
For a sunken or partially submerged vessel, divers or marine crew may need to inspect the hull and identify suitable positions for the airbags. Where the vessel is being moved from a bank or shoreline, long cylindrical airbags can be placed beneath the hull to provide support and reduce friction as the vessel is moved.
Send It Marine also provides on-call commercial diving support for marine investigations and recovery works where underwater access or inspection is required.
How do airbags help recover a sunken boat?
In a vessel recovery, airbags may be used to introduce buoyancy gradually until the boat becomes easier to stabilise or reposition. The process can form part of a broader recovery plan that also includes rigging, pumping, crane support, work boats, or barges.
A typical recovery may begin with an inspection of the vessel and the surrounding area. Once the boat's condition and position are understood, suitable recovery points can be selected and the airbags can be placed where they will provide useful support.
Inflation can then be carried out in stages. As the vessel begins to rise or change position, the recovery team can reassess its balance and condition before progressing further. This controlled approach is important because water moving inside a flooded vessel or changes in the load can affect stability.
Our guide on how sunken boat recovery works explains the wider process, including inspections, cranes, work boats, environmental considerations, and what happens after the vessel reaches the surface.
Can marine airbags be used to launch or retrieve boats?
Yes. Long cylindrical marine airbags can also be used to support vessels during launching or retrieval from a bank, slip area, or shoreline. Instead of relying entirely on a fixed slipway or heavy lifting equipment, the airbags can create a rolling support surface beneath the hull.
As the vessel moves, the airbags can help distribute the load and reduce direct contact between the hull and the ground. The setup still needs to account for the vessel's weight, hull shape, gradient, surface conditions, and the available pulling or control equipment.
This application can be particularly useful where conventional launching infrastructure is limited, but it should still be treated as a planned marine operation rather than simply placing inflatable bags under a boat and moving it.
What is the difference between marine recovery airbags and underwater lift bags?
The terms are sometimes used loosely, but there are practical differences between the equipment types.
Marine recovery or ship-launching airbags are often long cylindrical bags designed to support large areas of a vessel, provide flotation, or act as rollers during movement. They can be used for launching, retrieving, refloating, or supporting vessels and marine structures.
Underwater lift bags are usually attached to a submerged object or load and inflated to create vertical lift. They are commonly used in commercial diving, subsea construction, equipment recovery, and marine salvage.
Australian suppliers of underwater lift bags describe applications ranging from wreck and equipment recovery through to underwater construction and subsea positioning. The right system depends on whether the project requires vertical lifting, distributed vessel support, controlled flotation, or shore-based movement.
What can marine recovery airbags be used for?
Marine airbags are not limited to recovering sunken boats. Depending on the equipment and project requirements, they can support a range of marine and civil applications.
Common uses can include:
- sunken vessel and object recovery
- refloating stranded or grounded vessels
- launching boats from shore or a bank
- retrieving vessels onto shore
- supporting floating structures during installation
- assisting with marine construction works
- providing temporary buoyancy to marine assets
- supporting mooring, buoy, jetty, or bridge-related works
Send It Marine's marine recovery airbags are listed for applications including launching and retrieving vessels from the bank or shore and recovering sunken vessels or objects. The company's current equipment pages list the bags at approximately 1.2 metres by 10 metres.
Why might airbags be used instead of a crane?
Airbags and cranes solve different problems. A crane provides direct mechanical lifting, while airbags create buoyancy or distributed support. Some recoveries are better suited to one method, while others use both.
Airbags may be useful where crane access is limited, where a vessel needs to be refloated rather than completely lifted from the water, or where support needs to be distributed across a larger section of the hull. They can also help reduce the load that another lifting system needs to manage.
A crane may be more appropriate where the asset needs to be lifted directly onto a barge, trailer, or shore-based area. Send It Marine also has marine crane capability for projects where direct lifting forms part of the recovery plan.
What factors determine how many airbags are needed?
There is no standard number of airbags for every recovery. The required setup depends on the load and how the buoyancy needs to be distributed.
Factors can include:
- the vessel's size and estimated weight
- how much water is inside the vessel
- the hull shape and structural condition
- whether the boat is upright, on its side, or grounded
- water depth and current
- the amount of buoyancy required
- where the airbags can be positioned safely
- whether cranes, pumps, winches, or work boats are also being used
- how the vessel will be moved after it is stabilised
A damaged vessel can also behave differently as it rises. The weight distribution may change as water drains or loose materials move, which is why recovery setups are generally reassessed as the operation progresses.
What equipment may be used with marine recovery airbags?
Airbags are often one part of a larger marine recovery system. Supporting equipment can help with access, inspection, inflation, positioning, lifting, and final removal.
Depending on the project, the recovery setup may include commercial divers, compressors, rigging, pumps, work boats, barges, winches, towing equipment, or cranes. A work boat can provide access and carry crew or equipment, while a larger barge can create a stable working platform for heavier operations.
This is why the recovery method should be selected after the site and vessel have been assessed. The aim is to combine only the equipment needed for the job rather than assuming every recovery requires the same setup.
Are marine airbags only used in deep water?
No. One advantage of long cylindrical vessel recovery airbags is that they can also be used around shorelines, banks, launching areas, and shallow water. Their role may be more about supporting or moving the vessel than lifting it vertically through deep water.
In very shallow water, long bags can sometimes be more practical than tall underwater lift bags because there may not be enough vertical clearance for a conventional suspended lift system. The exact approach still depends on the vessel, the available space, and the surface beneath it.
What should be assessed before using marine recovery airbags?
Before airbags are deployed, the recovery team needs to understand both the load and the environment. This includes checking the vessel condition, likely weight, water depth, access, surrounding infrastructure, and potential environmental hazards.
Useful project information can include photographs, vessel dimensions, the location of the incident, the approximate water depth, the position of the boat, known damage, and whether fuel or other materials are on board.
Providing that information early can help determine whether airbags are a suitable option and what other equipment may need to be mobilised.
Marine recovery airbags for South Australian projects
Send It Marine provides marine recovery and lifting support across South Australia, including regional and remote waterways. Its marine recovery capability includes specialised airbags, commercial diving support, work boats, barges, and marine lifting equipment that can be combined according to the project requirements.
If you are comparing recovery methods for a sunken, stranded, or difficult-to-move vessel, explore our marine airbag recovery services to see where this equipment can be used.
For a project-specific assessment, contact the Send It Marine team with the vessel details, location, photographs, and any known information about the incident. These details provide a practical starting point for discussing whether airbags, lifting equipment, work boats, or a combined recovery method may be suitable.
