Lifting Bags, Shot Lines and Decompression Stations

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

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

3. 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! DUSAC -Advanced Diving Techniques

4. 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 DUSAC -Advanced Diving Techniques

5. Buoy Line Shot weight 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 • Disadvantages • More complicated! • Risk of line tangling • Bottom Tensioned Shot Line not often used DUSAC -Advanced Diving Techniques

6. Counterweight 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 DUSAC -Advanced Diving Techniques

7. 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 Line 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 Shot Line Construction DUSAC -Advanced Diving Techniques

8. 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 DUSAC -Advanced Diving Techniques

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

10. 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 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! DUSAC -Advanced Diving Techniques

12. 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 DUSAC -Advanced Diving Techniques

13. 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 DUSAC -Advanced Diving Techniques

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