A liftbag may be used in several ways and is a useful underwater tool; however, perhaps its most common use is as a signal marker to show surface support — such as a liveboat captain — the dive team’s position in the water during free and drifting ascents. It is this use that the following procedure will outline. This procedure will be taught to you as part of your Techdivertraining TDI program.
(Assumes use of safety sausage type marker connected to open-faced spool containing more than 20 metres (70 feet) of #36 braided nylon knotted every 3 meters or ten feet)
A Surface Marker Buoy (SMB) or sausage-type liftbag is the most effective way to signal a team’s position in the water during an ascent away from a fixed ascent line in still water or during a drifting deco. The sealed or semi-sealed bags are preferred to an open-ended bag since this design can deflate when it’s on the surface in moderately rough seas. SMBs and liftbags should be brightly colored (but NOT white) and need to be marked to conform to any local regulations. In addition, it helps when diver’s name is written somewhere near the bag’s top with Sharpie-type marker.
Team deployment: single marker
Unless you are doing a skills session as part of your inwater assessment, it’s usual to deploy only one marker per dive team. This is often done when the team has reached relatively shallow water; usually sometime following any gas switch at 21 metres (70-feet).
Dive leader signals Deploy Marker and team members confirm. Each member should carry a marker and a spool but part of the dive briefing will have covered of whose marker and spool is to be deployed This team member will remove the spool and marker from her pocket or pouch, and display it for team to see. If the spool and marker are not pre-attached, she will do so and then hand the spool to her dive buddy. He will confirm that the line from the spool is firmly attached but ready to let out line unhindered and giving his buddy the OK” signal, will continue to hold on to the spool. She will confirm this signal. After a final check to see that the line is not fouling any equipment, she will begin to inflate the marker (see below for suggested methods). When it has sufficient gas to rise towards the surface she will hold the bag away from her body and in the center of the buddy circle, Her team members will give the OK” signal and she will then release the bag. The spool may be held lightly with the fingers or may be left to unroll itself freely in the water column. When the marker reaches the surface, the line is tightened and re-clipped to prevent the spool from dropping into the depths.
The spool may be left in the center of the buddy circle providing a good visual reference. The spool’s owner is usually responsible for rewinding line as the team continues its ascent, although this task can be shared. At no point is a spool or reel attached to an SMB to be clipped or tied to a diver.
Team deployment: multiple markers
Putting more than one bag and line up usually means the exercise is part of a skills session. In this case, deployment is done individually (see procedure below). However, each diver waits her turn to deploy her bag. DON’T try to throw several bags to the surface at once. You’ll simply end up with a bird’s nest of tangled lines.
Take spool and marker from pocket ensuring that line is firmly attached to marker. Hold spool in right hand and marker in left and show to buddy. They should confirm they have visually checked that you are clear to inflate. Begin to inflate marker until it is pulling lightly for the surface. Hold line and marker in front of you making sure no equipment is fouling the line. Watch for your buddy to give the OK signal and allow the marker to ascend.
A common mistake is over inflating a marker so that it is impossible to control at depth. Remember Boyle’s law. The second most common mistake is under inflating an SMB! To be effective as a marker, an SMB must float upright with at least its top half out of the water. This requires it to be filled with gas and for the diver below to put some downward force on the line. This will help keep the marker visible to surface support personnel.
There are several ways to fill an SMB. Semi-closed models can be filled by transferring gas from the wing into the bag using the LP (low-pressure) inflator/deflator. Additional gas can be added to the bag using the wing inflator but be careful to add gas in short spurts especially in cold water. Closed bags are inflated with an LP inflation hose. This can be a dedicated hose attached to a stage bottle or the drysuit hose can be disconnected from the suit, used to inflate the bag and then be reconnected.
Exhaling into a bag may work but it puts the bag and the line attached to it very close to the diver’s face and gear. Entanglement is a real possibility. Purging a spare regulator into a bag may work in warm water but can be a guaranteed way to start a freeflow.
Divers should practice bag deployment in shallow water when they have no decompression or safety stop obligation.
It’s vital that divers break surface no more than three meters from the marker especially where surface traffic or heavy seas may be a factor.
Diver alert markers can also be used to signal surface support that there is a problem with the dive team. Some advocate the use of different colored bags for this… I am not entirely comfortable with that option. I prefer instead the practice of sending a second marker up the same line. A message slate or note can be attached to the first or second bag explaining the problem. Naturally, whichever practice you opt to use, it is necessary to discuss this with your surface support prior to EVERY dive.
One last tip:
Knotting the line on a spool (say every three metres or ten feet) can help you measure things like the length of a hatch cover or how far you are from the surface Very handy and reassuring in low-vis situations, and required when you practice bag deployment with mask off or blacked out.