Normal diving procedures generally apply to diving in extremely cold environments. However, there are a number of significant equipment and procedural differences that enhance the diver's safety.
11-2.1 Planning Guidelines. The following special planning considerations relate to diving under/near ice cover or in water at or below a temperature of 37°F:
■ The task and requirement for ice diving should be reviewed to ascertain that it is operationally essential.
■ Environmental conditions such as ice thickness, water depth, temperature, wind velocity, current, visibility, and light conditions should be determined. Ideally, a reconnaissance of the proposed dive site is performed by the Diving Supervisor or a person with ice-covered or cold water diving experience.
The type of dive equipment chosen must be suited for the operation.
■ Logistical planning must include transportation, ancillary equipment, provisioning, fuel, tools, clothing and bedding, medical evacuation procedures, communications, etc.
NOTE The water temperature of 37°F was set as a limit as a result of Naval Experimental Diving Unit's regulator freeze-up testing. For planning purposes, the guidance above may also be used for diving where the water temperature is above 37°F.
11-2.2 Navigational Considerations. Conditions in cold and ice-covered water affect diver underwater navigation in the following ways:
■ The proximity of the magnetic pole in polar regions makes the magnetic compass useless.
■ The life of batteries in homing beacons, strobes, and communication equipment is shortened when used in cold water.
Surface light is so diffused by ice cover that it is nearly impossible to determine its source.
Direct ascent to the surface is impossible when under the ice and determining return direction is often hindered.
In shallow ice-covered waters, detours are often required to circumvent keels or pressure ridges beneath the ice.
With an ice cover, there are no waves and therefore no ripple patterns on the bottom to use for general orientation.
11-2.3 Scuba Considerations. Scuba equipment has advantages and disadvantages that should be considered when planning a cold water dive.
The advantages of using scuba are:
Portability Quick deployment
Minimal surface-support requirements
The disadvantages of using scuba are:
Susceptibility of regulator to freezing Depth limitations Limited communications
Severely limited ability to employ decompression diving techniques Duration limitations of CO2 removal systems in closed-circuit UBA
11-2.4 Scuba Regulators. Refer to the ANU for selection of proper regulator. The single-hose regulator is susceptible to freezing. The first and/or second stage of the single-hose regulator may freeze in the free-flow position after a few minutes of exposure in cold water. The single-hose regulator should be kept in a warm place before diving. It is important that the diver test the regulator in a warm place, then refrain from breathing it until submerging. When returning to the surface, the regulator should remain submerged and the diver should refrain from breathing from the regulator until resubmerging. The diver's time on the surface should be kept to a minimum. Once under the water, chances of a freeze-up are reduced. However, if a regulator is allowed to free-flow at depth for as little as five seconds, freeze-up may occur. The diver should therefore avoid purging the second stage of the regulator when diving in cold water. If water needs to be purged from the mouthpiece, the diver should do so by exhaling into it (Figure 11-1).
11-2.4.1 Special Precautions. Single-hose regulators should be equipped with an antifreeze cap, which is a special first-stage cap that can be filled with liquid silicone available from the manufacturer. Correct maintenance and application of an approved lubricant to the appropriate points are also essential. Extra precautions must also be taken to make sure that scuba cylinders are completely dry inside, that moisture-free air is used, and that the regulator is thoroughly dried prior to use.
11-2.4.2 Octopus and Redundant Regulators. Where water temperature is at or below 37°F, a redundant scuba system (twin scuba bottles, each having a K-valve and an approved cold water regulator) or twin scuba bottles with one common manifold and an approved cold water regulator (with octopus) shall be used.
11-2.5 Life Preserver. The use of life preservers is prohibited only when diving under ice. The accidental inflation of a life preserver will force the diver upward and may cause a collision with the undersurface of the ice. Should the diver be caught behind a pressure ridge or other subsurface ice structure, recovery may be difficult even with tending lines. Also, the exhaust and inlet valves of the variable volume dry suit will be covered if a life preserver is worn. In the event of a dry suit blowup, the inability to reach the exhaust dump valve could cause rapid ascent and collision with the surface ice.
11-2.6 Face Mask. The diver's mask may show an increased tendency to fog in cold water. An antifog solution should be used to prevent this from occurring. Saliva will not prevent cold water fogging.
11-2.7 Scuba Equipment. The minimum equipment required by every Navy scuba diver for under-ice operations consists of:
Wet suit/variable volume dry suit
Open-circuit scuba with cold water modification or closed-circuit UBA Face mask
Weight belt and weights as required
Knife and scabbard
Submersible scuba bottle pressure gauge ■ Harness such as an Integrated Divers Vest (IDV), MK 12 jocking harness, etc. Lifelines
A variety of special equipment, such as underwater cameras and lift bags, is available to divers [see the NAVSEA/00C Authorized for Navy Use (ANU) list for specific identification of authorized equipment]. However, the effect of extreme cold on the operation of special equipment must be ascertained prior to use.
11-2.8 Surface-Supplied Diving System (SSDS) Considerations. Using SSDS in ice-covered or cold water requires detailed operations planning and extensive logistical support. This includes thermal protection for an elaborate dive station and recompression chamber and hot water heating equipment. In addition, dive equipment may require cold climate modification. Because of logistical considerations, scuba is used in most ice diving situations. However, SSDS may be required because of prolonged bottom times, depth requirements, and complex communications between topside and diver. When diving in cold water that is not ice covered, logistic and equipment support requirements are reduced; however, very cold water poses many of the same dangers to the surface-supplied diver as ice diving.
11-2.8.1 Advantages and Disadvantages of SSDS.
The advantages of using SSDS are:
Configuration supports bottom-oriented work.
Hot water suit and variable volume dry suit offer diver maximum thermal and environmental protection.
Communications cable offers audio communications.
Gas supply allows maximum duration to the maximum depth limits of diving.
The disadvantages of using SSDS are:
■ Manifold/panel may freeze up.
Low-pressure compressors do not efficiently remove moisture from the air which may freeze and clog filters or fracture equipment. This is more likely when the water is very cold and the air is warm. Banks of high-pressure cylinders may have to be used.
Buildup of air or gas under the ice cover could weaken and fracture thin ice, endangering tenders, other topside personnel, and equipment.
■ Movement of ice could foul or drag diver's umbilical. Battery life of electronic gear is severely reduced.
Carbon dioxide removal recirculator components may have to be heated.
Decompression under extreme cold conditions may be dangerous due to water temperature, ice movement, etc.
11-2.8.2 Effect of Ice Conditions on SSDS. Ice conditions can prevent or severely affect surface-supplied diving. In general, the ice field must be stationary and thick enough to support the dive station and support equipment. If the dive must be accomplished through an ice floe, the floe must be firmly attached to land or a stable ice field. Severe ice conditions seriously restrict or prohibit surface-supplied diving through the ice (i.e., moving, unstable ice or pack ice and bergs, and deep or jagged pressure ridges could obstruct or trap the diver). In cases where a diver is deployed from a boat in a fixed mooring, the boat, divers, and divers' umbilicals must not be threatened by moving ice floes.
11-2.9 Suit Selection. Custom wet suits designed for cold water diving, variable volume dry suits, and hot water suits have all been used effectively for diving in extremely cold water. Each has advantages and disadvantages that must be considered when planning a particular dive mission. All suits must be inspected before use to ensure they are in good condition with no seam separations or fabric cuts.
11-2.9.1 Wet Suits. Custom wet suits have the advantages of wide availability, simplicity and less danger of catastrophic failure than dry suits. Although the wet suit is not the equipment of choice, if used the following should be considered:
The wet suit should be maintained in the best possible condition to reduce water flushing in and out of the suit.
■ Wearing heavy insulating socks under the boots in a wet suit will help keep feet warm.
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