This document provides an overview of cave diving environments and characteristics divers need to understand, including: - Water make-up such as tannic water which stains visibility red, and hydrogen sulfide layers which are toxic and turn equipment black. - Haloclines, which are the interfaces between salt and fresh water layers, can distort visibility when disturbed. - Other factors like bottom conditions of sand, mud or clay, and water contamination risks are discussed. Understanding the cave environment is important for safe diving.

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CCR Cave Diving “Almost Simplified”
CCR Cave Diving
“Almost Simplified”
As There Is Nothing
Simple About
Cave Diving
A Complete Guide to Diving a
Closed Circuit Rebreather in
the Overhead Environment
By Dr. Mel Clark

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CCR Cave Diving “Almost Simplified”
www.Silent
Table of Contents
Chapter #1 Introduction
• Introduction.........................................
CCR rules............................................•
Cave rules............................................•
CCR cave rules....................................•
Acknowledgements.............................•
Chapter #2 The Cave Diving Environment
Cave Types..........................................•
Dissolution..........................................•
Coral....................................................•
Sea.......................................................•
Lava.....................................................•
Glacial.................................................•
Cave Descriptive Terminology............•
Speleotherm.........................................•
Vadose cave.........................................•
Phreatic cave.......................................•
Spring..................................................•
Siphon.................................................•
No flow................................................•
Sinks....................................................•
Sump...................................................•
Characteristics of Caves......................•
Bottom conditions...............................•
Sand.....................................................•
Mud.....................................................•
Clay.....................................................•
Water Make Up...................................•
Tannic water........................................•
Hydrogen sulfide.................................•
Haloclines............................................•
Water Contamination...........................•
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CCR Cave Diving “Almost Simplified”
Chapter #3 CCR Cave Diving Equipment
CCR...................................................•
Off-board gas....................................•
Harness & BCD................................•
Weights.............................................•
Bailout and stage cylinders...............•
Bailout regulators..............................•
Lights................................................•
Reels/spools......................................•
Markers..............................................•
Directional.........................................•
Non-directional..................................•
Tools..................................................•
Mask and fins....................................•
Chapter #4 Cave Diving Hazards Exposed
Springs..............................................•
Siphons.............................................•
Tidal flow..........................................•
No flow.............................................•
Restrictions.......................................•
Minor.................................................•
Moderate...........................................•
Major.................................................•
Poor visibility....................................•
Line traps..........................................•
Cave visibility...................................•
Haloclines.........................................•
Tannic water hydrogen sulfide..........•
Entanglement....................................•
Entrapment........................................•
Depth.................................................•
Distance............................................•
Guideline breakage...........................•
Equipment failure.............................•
Other divers.......................................•
Psychological cave hazards.............•
Over confidence................................•
Reasons for cave diving fatalities.....•
Trained cave diver deaths..................•
Non-trained cave diver deaths...........•
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CCR Cave Diving “Almost Simplified”
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Chapter #5 Cave Diving Skills
Pre-Dive.................................................................•
Build and confirmation..........................................•
Site evaluation and CCR equipment confirmation.•
Turn points evaluation and dive plan.....................•
In water check and equipment matching................•
Communication......................................................•
Command signals...................................................•
Handsignals............................................................•
Number signals.......................................................•
Lightsignals............................................................•
Written communication..........................................•
Touch communication............................................•
Cave navigation......................................................•
Mainline.................................................................•
Off-shoot line.........................................................•
Jump.......................................................................•
Gap.........................................................................•
T-intersection..........................................................•
Primary reel............................................................•
Safety reel..............................................................•
Jump/gap reel.........................................................•
Line trap.................................................................•
Tie-off.....................................................................•
Placement...............................................................•
Cookies or clothes pins..........................................•
Two line arrows pointing in the same direction.....•
Two line arrows pointing in opposite directions....•
Line skills...............................................................•
Team positioning....................................................•
Making jumps........................................................•
Working around lines.............................................•
Traverse..................................................................•
Circuits...................................................................•
Exiting and passing................................................•
Swimming..............................................................•
Modified frog kick.................................................•
Modified flutter kick...............................................•
Pull and glide.........................................................•
Shuffle kick............................................................•
Cave diving awareness...........................................•
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CCR Cave Diving “Almost Simplified”
Chapter #6 Cave Diving Adverse Situation
Cave Specific Adverse Situation.....................................•
Lost line...........................................................................•
Broken line......................................................................•
Inadvertent jump.............................................................•
Loss of navigational awareness.......................................•
Blackout situations..........................................................•
Lost buddy.......................................................................•
Lost light.........................................................................•
Line entanglement...........................................................•
Entrapment.......................................................................•
CCR failure.....................................................................•
Loss of buoyancy device.................................................•
Sharing air.......................................................................•
CCR Specific Adverse Situations “A Brief Overview”...•
Feeling funny...................................................................•
The first response.............................................................•
BOascent.........................................................................•
The three H’s...................................................................•
Hyperoxia........................................................................•
Hypoxia............................................................................•
Hypercapnia.....................................................................•
Floods..............................................................................•
SCR mode.......................................................................•
Off-board gas..................................................................•
Open loop........................................................................•
Boom...............................................................................•
What if game...................................................................•
Oxygen cell issues...........................................................•
PO2issues........................................................................•
Display issues..................................................................•
OC BO supply issues.......................................................•
Buddy rescue/recovery....................................................•
Omitted decompression...................................................•
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CCR Cave Diving “Almost Simplified”
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Chapter #7 Cave Dive Planning
Cave Specific Dive Planning...........................•
Site deposition.................................................•
Dive objectives................................................•
Four CCR turn around points..........................•
On-board oxygen.............................................•
On-board diluent..............................................•
Scrubber...........................................................•
Bailout gas.......................................................•
Stage gas..........................................................•
Mixed teams....................................................•
Cave Non-specific Dive Planning...................•
Oxygen toxicity...............................................•
Inert gas loading calculations..........................•
Example CCR dive plan mainly one depth.....•
Example CCR dive plan mainly two depths....•
Chapter #8 Cave Psychology and Survival
Stressors on a dive...........................................•
Distance...........................................................•
Confinement.....................................................•
Physical stress..................................................•
Doubting navigation.........................................•
Time pressure...................................................•
Task loading.....................................................•
High flow.........................................................•
Peer pressure....................................................•
Ego pressure.....................................................•
Dealing with stress...........................................•
Recognizing stress in your buddy....................•
Choosing your buddy.......................................•
Final thoughts..................................................•
References..................................................................
About the author.........................................................
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CCR Cave Diving “Almost Simplified”
Chapter 1: Introduction
Introduction
Course overview
Photo by Curt Bowen
Introduction
CCR rules
Cave rules
CCR cave rules
Acknowledgements

8. 8 ©SilentScuba 2010 Rev. 1.0
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Chapter 2 : The Cave Environment
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Chapter 2: The Cave Environment
Cave Types
Dissolution
Coral
Sea
Lava
Glacial
Mines and other manmade
Cave Descriptive Terminology
Speleotherm
Vadose cave
Phreatic cave
Spring
Siphon
No flow
Sinks
Sump
Characteristics of Caves
Bottom conditions
Sand
Mud
Clay
Organic & biological material
Water Make Up
Tannic water
Hydrogen sulfide
Haloclines
Hydrogen sulfide
Haloclines
Water Contamination

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9 ©SilentScuba 2010 Rev. 1.0
Chapter 3 : CCR Cave Diving Equipment
Chapter 3: CCR Cave Diving Equipment
CCR
Off-board gas
Harness & BCD
Weights
Bailout and stage cylinders
Bailout regulators
Lights
Reels/spools
Markers
Directional
Non-directional
Tools
Mask and fins

10. 10 ©SilentScuba 2010 Rev. 1.0
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Chapter 4 : Cave Diving Hazards Exposed
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Chapter 4: Cave Diving Hazards Exposed
Springs
Siphons
Tidal flow
No flow
Restrictions
Minor
Moderate
Major
Poor visibility
Line traps
Cave visibility
Haloclines
Tannic water hydrogen sulfide
Entanglement
Entrapment
Depth
Distance
Guideline breakage
Equipment failure
Other divers
Psychological cave hazards
Over confidence

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11 ©SilentScuba 2010 Rev. 1.0
Chapter 5 : Cave Diving Skills
Chapter 5: Cave Diving Skills
Pre-Dive
Build and confirmation
Site evaluation and CCR equipment confirmation
Turn points evaluation and dive plan
In water check and equipment matching
Communication
Command signals
Hand signals
Number signals
Light signals
Written communication
Touch communication
Cave navigation
Mainline
Off-shoot line
Jump
Gap
T-intersection
Primary reel
Safety reel
Jump/gap reel
Line trap
Tie-off
Placement
Cookies or clothes pins
Two line arrows pointing in the same
direction
Two line arrows pointing in opposite
directions
Line skills
Team positioning
Making jumps
Working around lines
Traverse
Circuits
Exiting and passing
Swimming
Modified frog kick
Modified flutter kick
Pull and glide
Shuffle kick
Cave diving awareness

12. 12 ©SilentScuba 2010 Rev. 1.0
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Chapter 6 : Cave Diving Adverse Situation
www.Silent
Chapter 6: Cave Diving Adverse Situation
Cave Specific Adverse Situation
Lost line
Broken line
Inadvertent jump
Loss of navigational awareness
Blackout situations
Lost buddy
Lost light
Line entanglement
Entrapment
Loss of buoyancy device
Sharing air
CCR Specific Adverse Situations “A Brief Overview”
Feeling funny
The first response
BO ascent
The three H’s
Hyperoxia
Hypoxia
Hypercapnis
Floods
SCR mode
Off-board gas
Open loop
Boom
What if game
Oxygen cell issues
PO2 issues
Display issues
OC BO supply issues
Buddy rescue/recovery
Omitted decompression

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13 ©SilentScuba 2010 Rev. 1.0
Chapter 7 : Cave Dive Planning
Chapter 7: Cave Dive Planning
Cave Specific Dive Planning
Site deposition
Dive objectives
Four CCR turn around points
On-board oxygen
On-board diluent
Scrubber
Bailout gas
Stage gas
Mixed teams
Cave Non-specific Dive Planning
Oxygen toxicity
Inert gas loading calculations
Example CCR dive plan mainly one depth
Example CCR dive plan mainly two depths

14. 14 ©SilentScuba 2010 Rev. 1.0
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Chapter 8 : Cave Psychology and Survival
www.Silent
Chapter 8:Cave Psychology and Survival
Stressors on a dive
Distance
Confinement
Physical stress
Doubting navigation
Time pressure
Task loading
High flow
Peer pressure
Ego pressure
Dealing with stress
Recognizing stress in your buddy
Choosing your buddy
Final thoughts

15. tScuba.comtScuba.com
15 ©SilentScuba 2010 Rev. 1.0
Chapter 2 : The Cave Environment
Other characteristics the diver needs to understand is the water make up. Tannic water has a
reddish color to it. When the tannic level is high this water is next to impossible to see through.
Tannis comes from decomposing roots and bark. They also make for incredible photo oppor-
tunities. Hydrogen sulfide is a yellowish / brown layer in the water and usually occurs at the
interface between fresh and marine water layers. For hydrogen sulfide to be made, the layer
must be anoxic meaning there is no oxygen left in the water, then bacteria which are anaerobic
degrade plant and animal sediment producing the gas hydrogen sulfide. This gas is highly flam-
mable and quite toxic. As a diver passing through a hydrogen sulfide layer you are really at little
risk of the toxic effects as you are not breathing it in. Even so, I never hang around too long in
this layer. Some divers report a rotten egg like smell. Also, any brass you have will turn black
after being exposed to a hydrogen sulfide layer. In very high concentration, the hydrogen sul-
fide can burn your skin. If you surface in a hydrogen sulfide filled air space do not breathe the
gas, stay on your CCR. This is always solid advice when unsure of the air environment found
in air pockets in cave systems. Angelita Cenote in Mexico and Hospital Hole sink in the Weeki
Wachee river in Florida, are good examples of dive sites with a hydrogen sulfide layer. Sink
holes near the coast are most likely to have hydrogen sulfide due to the salt water intrusion.
As a diver you need to be most concerned with haloclines. A halocline is the interface between
salt and fresh water. The fresh water has a lower density and will sit on top of the more dense
salt water layer. There is a distinct interface between the two layers making it look like a mir-
ror in some cases. The thickness of the interface can range from inches to feet. This interface
when disturbed can completely distort visibility. When you encounter a halocline it is best to
swim above or below the interface so you don’t distort the visibility. If this is not possible then
swimming in a more side by side manner will allow the following divers to have some visibility.
The nice thing about the halocline is it settles relatively quickly and visibility will be restored.
Jo above the hydrogen sulfide layer, Erik below in
the hydrogen sulfide layer
Erik working on getting
above the hydrogen
sulfide layer

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Chapter 3 : CCR Cave Diving Equipment
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Markers
There are two main types of markers, directional and non-directional. A directional marker
points to the direction of the exit. The directional markers are called line arrows. Line arrows are
installed on permanent lines in the cave, they can also be marked with the distance to the nearest
air hole or exit. Divers will also carry at least three line arrows on each dive.All of your line arrows
need to be permanently marked to identify they are yours. Line arrows are employed at jumps,
line intersections or end of the line where navigational errors could occur. They take the guessing
out of the equation on exiting when used correctly. They can also be used in an emergency such
as in a lost line situation. In this case the diver would attach a line arrow to the permanent line
pointing in the direction they are exiting when they re-locate the line. This is important since their
buddy may stumble along this arrow and now they know one of two things; their buddy is ahead
of them and is safely exiting, or their buddy is lost and heading in the wrong direction, in this case
the buddy diver will need to access their turn points and decide to go after them or retreat. Emer-
gency use of line markers will be covered in Chapter 6, Cave Diving Adverse Situation Skills.
Another use for your line arrows is when you install a jump off a mainline and there is no arrow
already there then you must place an arrow on the main line pointing in the exit direction. This
arrow will help you know the correct way out and will also serve to hold your jump line in place.
Non-directional markers do not point towards an exit,
they serve to mark points such as maximum penetration
distances and help the diver complete circuits. Non-di-
rectional markers can also be used to mark the exit side
of confusing intersections and permanent line arrows.
The use of markers will be covered in Chapter 5, Cave
Diving Skills. Cookies and clothespins are considered
non-directional markers. Each diver should carry at least
one non-directional marker but this will depend on the
diving location. Mexican caves have many intersections
where the diver will require non-directional markers
and in this case a minimum of six should be carried.
Josh takes note of the arrows pointing in
opposite directions in Peacock Springs, Florida
Josh Places a cookie on the line
Markers attached to
a bungee.

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Chapter 5 : Cave Diving Skills

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