Techniques for Group Diving in UK Sumps

||Techniques for Group Diving in UK Sumps

This review is aimed at UK side mount diving on air and seeks to provide guidance on how to adapt established team diving techniques to UK conditions for divers who normally dive solo. The information contained in this review is not intended as a substitute for the team diving techniques typically used in larger sumps by other organisations abroad. Owing to the nature of UK style sumps, Team Diving in it’s true form is difficult for the Cave Diving Group to train for and implement. This document therefore refers to ‘Group Diving’ in reference to two or more divers in the water at the same time. Group diving can offer greater safety in some situations and is already used by the CDG, most notably during training and experience building dives, and for some exploration dives. Group diving has advantages in some situations but is not appropriate for all UK sumps. If the dive site is of low visibility or small passage a solo approach is better suited.

Team diving is not within the specific training remit of the CDG. The group diving techniques described in this technical review are not a substitute for team diving skills and must not be used in a team diving situation with trained team divers. The exact details of team diving techniques vary between areas/agencies. Any diver wishing to dive as part of a team must learn the team techniques that apply specifically to the area/team.

Team diving or Group Diving?

A recent review and update of the CDG risk assessment along with a review of Project 2020 prompted an analysis of the frequency of solo dives versus multiple divers in the same sump. The analysis, based in dives recorded in the CDG NL, showed that divers work together frequently for a variety of reasons with the average being 2.05 divers present for each dive. The manual acknowledges (page 37) team diving and gives some basic guidance without any detail. This technical review is intended to provide the missing detail.

Multiple solo divers in a sump at the same time creates additional risks unless the divers are coordinated to avoid confusion. By learning from team diving methodology the group diving techniques listed in this document can reduce risks and avoid confusion.

Group diving can offer greater safety in some situations and is already used by the CDG, most notably during training and experience building dives. CDG divers typically use a side mounted, independent cylinder configuration that does not support gas donation for the majority of dives in the UK. That does not mean that team diving techniques should not be adopted in suitable situations. That said, team diving is not a replacement for individual competence, nor is it a method of dependence. It compliments the competence of each individual diver and when used in the right place, enhances redundancy, efficiency and safety.

What constitutes a team dive:

  • Divers must maintain visual or physical contact with each other.
  • Divers communicate with each other routinely using passive light signals, hand
  • signals or light signals.
  • Divers offer assistance to each other in the event of problems and emergencies.
  • Divers work together to achieve a goal.
  • Identical procedures, protocols, skill set, experience and knowledge.

Must haves for team diving to work:

  • Underwater communication skills.
  • Pre dive team briefing.
  • Division of tasks between divers as required for the specific objective of the dive. • Diving skills to protect visibility.
  • Diving skills to donate a breathing set including air sharing.
  • Familiarity with team members personal dive equipment configuration.

The advantages of team diving are:

  • More eyes – divers can spot problems for each other.
  • More brains – more possible answers to problems.
  • More hands – divers can help each other by problem solving and fixing issues.
  • More labour – a large job can be broken down into small individual tasks and distributed between team members.
  • More gas – gas reserves may be pooled, managed, handed off or fetched by a team member.

A group of CDG solo divers do not meet the requirements of a team dive as listed above but there is no reason why some of the advantages of team diving cannot be achieved for some dives. By adapting team diving techniques and adding them to the solo skill set divers working in a group will be better placed to help each other out should the need arise or combine their effort to achieve a complex task. The divers will still not be considered a team but they can be considered a group if they have and use the necessary skills. Each diver in the group will be a solo diver who can help other group members.

Dives that are most likely to benefit from a group diving approach:

  • Open water training dives.
  • Experience building dives in sumps.
  • Surveying dives when working to a high survey grade.
  • Underwater digging.
  • Transportation of large items of equipment through a sump. • Underwater filming (photography and videography).
  • Staging cylinders for longer/deeper dives.
  • Social diving.
  • Multiple divers passing the same sump to cave beyond.
  • Dives requiring large quantities of bailout gas.

Sumps that make it difficult to gain from the advantages of team diving are:

  • Tight sumps which limit access to other team members.
  • Short sumps where it is quicker to return to base to resolve a problem.
  • Sumps with very low or zero visibility where communication becomes very difficult.
  • Sumps with high flow where maintaining relative distance from team members may prove difficult.

Group diving principals.

Configuration changes.

UK cave diving requires a side mounted, independent cylinder configuration for the majority of sites. This configuration is not well suited to group diving so some level of alterations will be needed depending on the aim of the group dive and the skills of each diver in the group.

  • Long hose: One of the biggest advantages of team diving is the ability to donate gas. To facilitate this in a group diving situation a long hose that can be donated easily to another diver is carried on the right hand sidemount cylinder.
  • Hand held light: Helmet mounted lights make using light signals impractical and will dazzle other divers when attempting hand signals. A hand mounted light makes passive light signals and deliberate signalling easy. By directing helmet mounted lights downward or turning them off unless needed, dazzling can be avoided.
  • Brain: Group diving will need changes to the mindset of the solo diver not only in learning new skills but also in how to apply them to get the best advantage. This is easy to overlook but the solo mindset must be changed to fully support group diving.

Underwater communication skills.

  • To get access to some of the advantages of team diving, divers need to communicate. There are several methods, hand signals, light signals, touch and rebreather divers may attempt slow and clear enunciation of words into their breathing loop.
  • Hand signals can be difficult to read for a diver who is being dazzled by the signallers lights. Group members should direct their lights downwards towards the hand signals (or switch them off) and away from other group members eyes.
  • Light signals will be easier with a hand mounted or held light rather than relying on helmet mounted lights. In practice a mixture of the two signal types will be most useful, hand signals when group members are facing each other and light signals when the group is swimming along in line astern. Light signals are best created by directing a tightly focused beam on the floor of the sump underneath or slightly ahead of the diver in front. Passive light signals make it easier for the divers in front to communicate with those behind without having to turn and look. The movements available to signal clearly with a light are limited, a torch beam can be rotated clockwise and anticlockwise or moved in a straight line left to right or up and down.
  • Once divers can communicate effectively with each other they can work as a group to achieve an end goal but communication is clearly limited to a few agreed signals. More complex messages will need wetnotes. This is time consuming and can largely be avoided with a detailed pre-dive briefing so that each group member knows what their allocated role is on the dive.

Suggested hand signals:

  • End dive – one handed thumbs up as used in open water training.
  • Okay – as used in open water training.
  • Problem – flat hand, rocking side to side.
  • Out of air – hand across the throat in a cutting movement.
  • Bubbles – repeatedly touch thumb and index fingers together to indicate gas leak in equipment.
  • Read your gauges – two fingers in the upward facing palm of the other hand.
  • Stop – one hand, fingers rolled over into palm that is facing the diver being signalled to stop.
  • You watch me (training dives) – one hand, point to the diver who needs to watch then point two fingers towards your mask and then point to yourself.
  • Repeat task or drill (training dives) – two hands, rotate hands around each other horizontally.
  • Shut your eyes (training dives) – one hand over mask, there must be an agreed eyes open signal usually a tap on the shoulder.
  • One handed numbers – 1 through five, front of hand; 6 through 9, back of hand.
  • What is your deco – clenched fist with raised little finger.

Suggested light signals:

  • Slow steady clockwise rotation – okay.
  • Slow steady left right horizontal sweep – attention.
  • Rapid up and down horizontal sweep – help/emergency. (Whatever gets the attention of other divers in the group.)

Suggested touch signals:

  • Tap on the shoulder – end drill and open your eyes.
  • Tap on the head – end dive.
  • Hold a hand – to guide a diver into touch contact with the line.
  • Hold a hand stationary on the line – stop moving.
  • Leg squeezes – push: go forward, pull: back up, squeeze: stop, loss of contact: stop, repeated squeezes: emergency.

Pre dive group briefing.

The pre dive briefing is where the individual divers form into a group with a shared objective. Without it there is no group. The briefing needs to be led by one person who will run through the proposed dive and check that all group members understand the plan and how they will work together to achieve the goal of the dive. On a social dive this may be as simple as a basic dive in to a point and returning in an established group order. On an underwater digging trip, the briefing may have to cover complex activities such as building scaffold supports or moving spoil away from the dig face.

This will include:

  • The objective of the dive.
  • Turn point or pressures.
  • Exit plan (this may include more than one option depending on circumstances especially when doing multi sump trips).
  • Line details including all junctions, air-bells, exit bearing, significant features and line condition.
  • Passage details including restrictions, passage conditions with regard to movement and visibility, depth, current, unstable sections and any known differences.
  • A detailed run through of underwater tasks including who will is responsible for each step.
  • Verify hand/light signals to be used on the dive paying particular attention to task specific signals.

Division of tasks between divers as required for the specific objective of the dive.

The need for division of tasks is highly dive dependent. For some dives it will be less task intensive, such as social dives or divers simply passing through a sump. For dives that will move equipment through a sump or carry out digging in the sump, task division will be a critical factor in the amount that is achieved on the dive.
  • Tasks are to be matched with each diver’s ability – Do not taskload anyone.
  • A task must have a clear beginning and end point, as overlapping tasks can create confusion.
  • Part of a task that requires interaction with other divers must be clearly defined.
Diving skills to protect visibility.
Protecting visibility is good when solo diving and critical when group diving. Loss of visibility effects the simplicity of light and hand communication.
  • Team divers need to take great care to use techniques that will not disturb silt and other deposits.
  • Divers must maintain good buoyancy and trim.
  • Divers must use appropriate propulsion techniques such as the flutter kick, frogkick or pull, pull and glide.
Gas sharing using a long hose.
The reason for team diving is assistance by the team members if required, in the event of a serious gas failure or contamination of the gas supply, a long hose that can be donated easily to another diver is carried on the right hand sidemount cylinder. The long hose is generally two meters in length and can be either stowed along the length of the cylinder or half stowed with the remainder hog looped around the divers neck. In the event of gas sharing being necessary the out of gas diver can swim next to the donating diver or if passage size is small the out of gas diver swims in front of the donating diver. The long hose gives the ability to pass restrictions whilst sharing gas. It’s highly recommended that divers maintain physical contact during gas sharing and the drill is practiced regularly.
Gas sharing by donating a breathing set.
The use of independent breathings sets by the CDG along with faulty breathing set drills makes a complete loss of gas very unlikely. The one situation which can easily create such a double breathing set failure is contaminated gas from a bad fill. In the UK, when only using two cylinders, gas contamination is likely to be noticed at the start of the dive or when the dive first gains depth. In this situation a team member can donate a breathing set if the size of the passage allows, the donating diver will be well within thirds.
  • Signal an emergency out of gas.
  • Team member donates a second stage.
  • Once the compromised diver is comfortable swap cylinders (steel cylinderssignificantly effect buoyancy so the donating diver may have to pick up the breathing set that the compromised diver removed to maintain buoyancy).
  • Exit.


Diving as a group requires some additional skills on top of the usual solo skills while at the same time maintaining these solo diving skills. Below is a list of the new skills needed for group diving along with some solo skills which divers can become complacent with when group diving.
  • All divers must be connected to dive base by a continuous line at all times.
  • The group must travel at the pace of the slowest member.
  • When one diver ends the dive all divers head out together.
  • All group members must use individual line markers at junctions.
  • Divers must not remove other diver’s junction markers.
  • All divers in the group must have the necessary communication skills.
  • All divers in the group must be able to dive without reducing the visibility.
  • Immediately prior to the dive all group members must take part in a detailed briefing to prepare the group to work together.
  • Communicate with each other during the dive, keep track of other group members.
  • Group members in need of help must remain still to allow other divers to easilyview, assess and resolve a problem.
  • If a group loses track of one of its members, stop perform a visual search, if that fails return along the line to dive base.
  • If a diver loses track of the rest of the group, stop perform a visual search, if that fails return along the line to dive base.
  • When passing a narrow section of passage the lead group member waits for the last diver to pass through it before proceeding.
  • Do not use small air-bells as a group, any oxygen in airspace will deplete quickly.
  • In the event of loss of visibility maintain contact with the line and continue the dive while attempting to re- establish contact with the other members of the group.
  • After passing a constriction all divers in the group must wait until the last diver is through and signals okay.
CDG. May 2024