Ice and Cold Water Diving
Source: US Navy Diving Manual
Polar regions and other cold weather environments are uniquely hostile to divers, topside support personnel, and equipment. Diving where ice cover is present can be extremely hazardous and requires special equipment as well as appropriate operating and support procedures. Awareness of environmental conditions, personnel and equipment selection, and adequate logistical support are vital to success and dive team safety.
PLANNING GUIDELINES
The following special planning considerations relate to diving under/near ice cover or in water at or below a temperature of 37 degrees Fahrenheit:
- 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 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.
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 for general orientation.
SCUBA REGULATORS
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.
Single-hose regulators should be equipped with an anti-freeze cap, which is a special first-stage cap that can be filled with iquid silicone available from the manufacturer. 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.
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.
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.
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 insulation socks under the boots in a wet suit will help keep feet warm.
- CAUTION: In very cold water, the wet suit is only a marginally effective thermal protective measure, and its use exposes the diver to hypothermia and restricts available bottom time. The use of alternative thermal protective equipment should be considered in these circumstances.
Variable volume dry suits provide superior thermal protection to the scuba diver in the water and on the surface. The level of thermal protection can be varied through careful selection of the type and thickness of long underwear. Dry suit disadvantages are increased swimmer fatigue due to suit bulk, possible malfunction of inlet and exhaust valve, and the need for additional weights for neutral buoyancy. Nevertheless, because of is superior thermal protection, the dry suit is an essential component of extremely cold water diving.
