Who has not been drawn to the romance, thrill, and fantasy of finding pirate treasure? Movies make recovering gold and precious gems look easy. Few of us will ever have the pirate treasure fantasy become a reality, but treasure comes in many forms. Lost weight belts, outboard motors, and shipwreck artifacts are more common treasures that may require using a lift bag. Divers wearing more than one tank should also carry a lift bag or similar redundant source of buoyancy in case of a BCD or wing failure.
Divers generally use lift bags to raise submerged objects to the surface. The lift bag is filled with gas until the object exhibits neutral buoyancy so divers can bring it to the surface with minimal exertion. The reduced exertion comes with hazards and risks that may lead to serious injury or loss of life. Divers must be competent with buoyancy control and understand the physics involved because they must multitask and control buoyancy for themselves and the object.
Lift bags come in many sizes and configurations. Sizing denotes how much lift each bag can provide. Some available configurations include open bottom, baffle, and pillow bags.
Open-bottom lift bags are the easiest to fill but can lose buoyancy if they ascend out of control and breach the surface. Baffle lift bags are like a surface marker buoy. The benefit of this configuration is that the bag will not lose buoyancy if tipped over at the surface. Pillow bags are the largest and require significantly more gas than the other styles. They are commonly used in commercial dive operations and require surface-supplied gas.
All lift bags should have an over-pressure valve to help prevent overexpansion and allow the diver more control during the lift. Regardless of the type, divers should be prepared to release gas from the lift bag during the ascent to compensate for the increase in gas volume as ambient pressure decreases. Divers involved in the lift should have cutting devices readily available for use in case entanglement occurs.
The bag’s lifting capacity should match the object’s weight. Multiple smaller bags require more teamwork than a single large bag but are a safer choice. Once divers have determined the correct lift bag capacity, they must consider the amount of gas required to complete the lift. Displacement and depth are part of the equation to determine lift needs.
Divers should carry a redundant gas supply for the lift instead of using their breathing gas. A redundant supply will allow the diver to retain their supply for breathing and eliminate having a primary or secondary regulator get entangled during the lift. Specialized air nozzles and slow-fill inflator assemblies are the preferred filling methods over a second stage. Those devices provide a more controlled gas release than purging a second stage.
Divers should inflate the bag by adding small amounts of gas and periodically checking to see if the object is nearing neutral buoyancy. They can fine-tune neutral buoyancy by adjusting the object’s position in the water column. Be sure to monitor the slightest unwanted ascent, and return the object to a deeper position to restore neutral buoyancy.
As a last resort, divers can puncture lift bags in the event of an out-of-control lift, but that could permanently damage the lift bag and endanger divers or elements of the environment below.
Rigging the lift is the most complex part of the salvage process. Buddy teams should carry a braided line with an eye spliced on each end. The line’s size and strength should be able to handle the stress of the lift. The line should not get frayed if rigged carefully, but using a cable instead of a line eliminates that concern. Divers should attach rigging lines to as many points of contact as possible to help distribute the object’s weight and reduce strain on the rigging line.
Shackles, carabiners, or bolt snaps can secure the rigging line to the object. All hardware should have a sufficient weight rating to handle the working load, and the object’s weight should be distributed evenly across all hardware. Wrapping the lift bag strap through the hardware multiple times helps with weight distribution.
Divers can use knots instead of metal hardware, but they must be able to tie the knots correctly and in zero visibility. Many possible knots exist, but the most useful is a bowline, which creates a temporary loop at the end of a line that will not tighten under load strain.
Dive teams need exceptional buoyancy control to preserve visibility as much as possible. An errant fin or lapse in focus can stir up the sediment where the object rests. The dangers the dive team faces intensifies significantly when visibility is reduced. The chance of diver entanglement increases, and securely rigging the object becomes more difficult.
The bottom composition can also create complexity with the lift due to the suction created. If you’ve ever lost a shoe in the mud, you know how difficult it is to pull it out. In many instances the lift will initially require more buoyancy to overcome suction. The object will be positively buoyant once freed and may ascend uncontrolled.
After making a salvage plan and entering the water, divers must maintain visual contact with each other and the object being lifted. Keep the area above the lift clear to avoid catching a diver and rocketing them to the surface if the lift begins an uncontrolled ascent. No one should be directly under the lift during the ascent either. If the rigging or lift bag fails, the object could injure a diver or pin them on the bottom.
The environment may dictate a positive buoyancy lift or a more controlled ascent. Divers can attach a line from a finger spool or reel to the lift to aid with surface retrieval or help locate the object if the lift fails, but doing so adds another element of difficulty for the dive team. To avoid entanglement, they must wind the line back on the spool or drum during the ascent.
Divers should avoid using their BCD or wing as a lift bag. It may be the easiest solution to retrieve an object, but it carries more risk. Without the additional ballast from the object, the diver will quickly become positively buoyant at depth and find themselves on the express elevator to the surface.
Light salvage can be a rewarding process if performed carefully. Practicing salvage dives in confined water can minimize the risks associated with these dives and ensure you will be ready to retrieve your treasure.
© Penyelam Siaga – Q2 2025
