Surface-supplied diving skills


Surface-supplied diving skills are the skills and procedures required for the safe operation and use of surface-supplied diving equipment. Besides these skills, which may be categorised as standard operating procedures, emergency procedures and rescue procedures, there are the actual working skills required to do the job, and the procedures for safe operation of the work equipment other than diving equipment that may be needed.
Some of the skills are common to all types of surface-supplied equipment and deployment modes, others are specific to the type of bell or stage, or to saturation diving. There are other skills required of divers which apply to the surface support function, and some of those are also mentioned here.

Basic skills

The basic skills and procedures of surface supplied diving are those skills that the diver may reasonably be expected to use during a dive when everything goes according to plan, and there are no emergencies. Many scuba skills are also common to surface supplied diving.

Preparing the surface supplied diving equipment

The work of setting up the diving equipment on site is generally done by all members of the diving team, and they are usually all expected to be competent at all aspects of this work. The work is supervised and quality control is the responsibility of the diving supervisor, but any specific item may be delegated to the divers and attendants in the team. Checklists are commonly used to ensure that nothing is omitted and indicate completion. Most equipment is function tested as far as practicable during setup, and may be rechecked when dressing in the diver, and again on entering the water, as some checks can only be done in the water. The work may be described under the following headings:
  • Setting up the gas supply – Main and backup breathing gas supply may be from a low pressure compressor, high pressure storage cylinders, manifolded banks of HP cylinders or large volume high pressure gas containers Gas is distributed to the divers from a gas panel, and umbilicals. The primary gas supply is set up and connected to the gas supply control manifold. The backup gas supply must also be connected to the gas panel so that it can be accessed with minimum delay. The divers' umbilicals must be connected up to the gas supply, blown through to ensure there are no contaminants, and connected to the helmet or full-face mask.
  • Setting up the Communications panel – Most surface supplied diving uses voice communications which is generally transmitted by a cable in the umbilical which must be connected to the helmet or full-face mask and to the communications panel at the surface and tested for function and quality of sound before use.
  • Checks of personal equipment include:
  • *That the bailout cylinders are fit for use, contain enough of the appropriate gas for the planned dive, and the cylinder valves function correctly.
  • *That the bailout regulators are correctly fitted to the cylinders, have no leaks when pressurised, and no visible damage that might affect function or safety.
  • *That the non-return valves for the surface supply gas connection on the bailout manifolds are functioning correctly.
  • The divers' helmets or full-face masks are connected to the umbilical main gas supply hose and communications cable, and that the gas supply and communications system are working correctly.
  • Setting up the stage or bell and its launch and recovery system.
  • Setting up the hot-water supply if applicable.
  • Setting up the decompression chamber if applicable.

    Dressing in the diver

Some surface supplied diving equipment is heavy and cumbersome, and the diver is usually assisted with dressing in by a diver's attendant, who is often also a diver, so the skills of assisting a diver to dress in are necessary for the diver. The equipment involved includes:
Pre-dive checks are done by the dive team as a group, with the tender and diver working together and reporting results to the supervisor. Most checks are done before the diver is committed to the water, but some can only be done with the diver in the water. Before a dive the equipment must be thoroughly checked that it is suitable for the dive and in good working order, particularly those components which are part of the life-support system – the breathing apparatus, which includes:
  • Non-return valve test.
  • Main air supply.
  • Bailout check.
  • Comms check.
  • Visual check of the diver – check that the diver is fully dressed for the dive, with zips closed, weights in place, harness fastened and umbilical connected to helmet and harness, and if applicable, to the hot-water suit.
In-water checks include:
  • Breathing gas flow.
  • Helmet or mask leaks.
  • Dry suit leak check.
  • Pneumofathometer bubble test.
  • Voice communications check with head immersed.

    Demisting the faceplate

Most demand helmets and bandmasks have a valve to provide free-flow gas to the diver from a manually operated by-pass valve which usually directs the gas-flow over the interior surface of the faceplate/viewport. This flow of gas will blow off large water droplets and evaporate small droplets and light condensation, leaving the viewport clear. Though it tends to be noisy and wasteful of gas, it is trivially simple to do, does not require much practice, and is not safety critical. It is also done often in cold water. Some free-flow helmets and a few models of full-face mask pass the inlet air over the faceplate as default, and are thereby self-defogging.

Clearing a flooded helmet or full-face mask

There are two ways to clear a demand helmet of water: The free-flow valve may be opened, or the purge button of the demand valve may be pressed, either of which will cause any water above the exhaust port to be driven out. The same procedures can be used on a full-face mask which has both of these facilities. Some full-face masks do not have a free-flow option, and they are cleared by purging.
Flooding of a free-flow helmet may be managed by increasing flow rate and either opening the neck seal with the fingers or tilting the head to allow the water to flow out through the exhaust port.

Adjusting the breathing resistance

The pressure of the breathing gas supply to a surface supplied diver is set at the gas panel, and does not automatically compensate for small depth changes the way most open circuit scuba first stages operate. To compensate for small variations due to moving around the workplace and variations in posture, the surface supplied demand helmet or full-face mask may be provided with a second stage valve spring tension adjuster screw, commonly referred to as "dial-a-breath", which allows the diver to make adjustments to compensate for these variations. The knob can usually control cracking pressure from free-flow through to quite hard to breathe, and will usually compensate adequately for depth variations in the order of tens of metres. This skill is also well practiced by most divers, and is used on most dives. The knob is usually first adjusted during the pre-dive checks, and after that whenever the diver feels the need.

Voice communication

Correct and effective voice communication is necessary for both safety and efficient underwater work. The skills are learned during training and exercised on almost every working dive. Voice communication protocols involve speaking clearly, providing the required information unambiguously and succinctly, checking that the information has been received and correctly understood, and taking turns to speak. This is basically the same as radio voice protocol for other purposes, but the vocabulary may vary according to the operational circumstances.

Loss of voice communications

Loss of voice communications is not a directly life-threatening situation, but the risk of not being able to deal with an emergency is greatly increased as the surface team is unable to monitor the condition of the diver effectively and the diver is severely limited in the ability to communicate a problem to the backup personnel, reducing the chances of prompt response in an emergency. The diver will generally communicate the problem to the surface by rope signals and abort the dive.

Rope signals

The original method of communication between diver and surface was by pull signals on the lifeline, and these remain a useful emergency backup system. Divers are trained in rope signals, but the set of signals may vary regionally. The US Navy and UK rope signals are different.

Umbilical management

There are two aspects of umbilical management: By the diver, and by the attendant. They work together to keep the umbilical from twisting, restraining the diver's movements, entanglement, and excess slack. The tender will control the amount of umbilical in the water, recover excess slack and coil it ready for further use. The tender may also be required to assist the diver's ascent by hauling in the umbilical at the correct rate to facilitate decompression, and by locking off/belaying at the decompression stops. When diving from a bell, the bellman is the tender to the working diver. When there is a significant risk of the umbilical becoming snagged on underwater obstructions, it may be necessary to use an underwater tender at those areas, or to guide the umbilical past obstructions by the use of some form of fairlead. A similar arrangement may be used to prevent the diver from approaching known hazards too closely. One way this can be done is to lower a large weighted hoop to a predetermined position, and for the diver to pass through this hoop on the way to the worksite.