1. Lifting Bags, Shot Lines and Decompression Stations
Andy Thomson

2. DUSAC -Advanced Diving Techniques
Introduction
Lifting Bags
Shot Lines
Types, Construction, Deployment and Retrieval
Decompression Stations
Types
October 25th, 2003
DUSAC -Advanced Diving Techniques

3. DUSAC -Advanced Diving Techniques
Lifting Bags
Types
Open Ended
Closed with valve
Self-inflating
When to Use
Retrieving items such as shot lines
When Not to Use
Taking items from wrecks that you shouldn’t be!
October 25th, 2003
DUSAC -Advanced Diving Techniques

4. DUSAC -Advanced Diving Techniques
Shot Lines
Why use a shot line
Marked entry/exit point - aids safe dive marshalling and boat cover
Shortest route to/from surface
More comfortable/secure
Datum point for searches
Why not use boat’s anchor?
Line moves with boat movement
Cover boat should be mobile at all times
DON’T DO IT
October 25th, 2003
DUSAC -Advanced Diving Techniques

5. DUSAC -Advanced Diving Techniques
Types of Shot Lines - 1
Simple Shot
Advantages - it’s simple!
Disadvantages
Not easily made vertical
Does not adjust for tidal rise/fall
Bottom-Tensioned Shot
Advantages – always vertical
More complicated!
Risk of line tangling
Bottom Tensioned Shot Line not often used
Buoy
Line
Shot weight
October 25th, 2003
DUSAC -Advanced Diving Techniques

6. DUSAC -Advanced Diving Techniques
Types of Shot Lines - 2
Top-tensioned Shot
Advantages
Adjusts for tidal rise/fall, provides near vertical line
Can give precise position of dive site
Disadvantages
More complex, counterweight tangle
Main part of line will move
Not ideal in current or wind
Counterweight
October 25th, 2003
DUSAC -Advanced Diving Techniques

7. Shot Line Construction
Thick enough to grip for recovery, usually about 12mm
Length
At least as long as it is deep
Plus a couple of metres
Surplus line
Needs to be kept tidy, better at the surface
Bouy
Enough bouyancy to support weight (50% more)
Weight – Heavy enough!
Counterweight
Approx. 5 – 10kg
Depends on conditions
Tide Bouy?
Small bouy to show current direction
October 25th, 2003
DUSAC -Advanced Diving Techniques

8. DUSAC -Advanced Diving Techniques
Shot Line Connections
Bouy, Line & Weights
Karabiners
Knots
Attachments
Karabiners
Short loops of cord or other ropes secured by
Prusik knots
Rolling Hitch
Shortening the line
Karabiners
Chain senneting, sheepshank
October 25th, 2003
DUSAC -Advanced Diving Techniques

9. Shot Line Deployment Once deployed, re-check!
Prepare before arrival at dive site!
Deploy on boat cox’n order only!
Think about direction of current!
Once deployed, re-check!
October 25th, 2003
DUSAC -Advanced Diving Techniques

10. DUSAC -Advanced Diving Techniques
Shot Line Recovery
Controlled Recovery
Lift bag bouyancy same or slightly less than weight of shot
Divers fill bag so it is neutrally bouyant or slightly negatively bouyant.
Lift to surface from boat, slowly pulling on line (can become uncontrolled)
Bouyant Recovery
Lift bag bouyancy greater than weight of shot
Divers fill bag to send it to the surface
Boat AND divers stay well clear
October 25th, 2003
DUSAC -Advanced Diving Techniques

11. Decompression Stations
A decompression station is simply a shot line that divers are carrying out stops on!
Methods of making this easier and safer are varied.
All require divers to return to the shotline for use.
Dives should be Planned Accordingly!
October 25th, 2003
DUSAC -Advanced Diving Techniques

12. DUSAC -Advanced Diving Techniques
Deco Stations – Types 1
Can be as simple as a loop tied into a shot line
Back-up deco cylinder – perhaps with Nitrox?
Lazy Deco Stations
Extra line, weight and bouy attached to main shot line
Back-up deco cylinder may be attached
Can be detached to drift with current - Requires Diver ‘logging’ system
October 25th, 2003
DUSAC -Advanced Diving Techniques

13. DUSAC -Advanced Diving Techniques
Deco Stations – Types 2
Decompression Trapeze
Requires two additional bouys, weights, lines and solid bars
Bars can be set-up at various or multiple depths.
Back-up deco cylinder may be attached if needed
Again, it can be detached to drift with current - Requires Diver ‘logging’ system
October 25th, 2003
DUSAC -Advanced Diving Techniques

14. DUSAC -Advanced Diving Techniques
Deco Stations – Types 3
Deco' Stops
48m
6 / 9m
- - -
24m
Recommended Stop
30Kgs
5 Kgs
Peg Board
CFT Extended Range Course
October 25th, 2003
DUSAC -Advanced Diving Techniques