Near-freezing water can change a diver’s physical abilities and behavior within a short time, creating hazards that may grow before the person fully recognizes them. A 2026 review warns that recreational divers entering polar seas face demands far beyond those found at many familiar warm-water sites.
The review, published in International Maritime Health on August 4, 2026, examines how extreme cold affects human physiology, behavior, safety and underwater performance. Author Christopher R. Kovacs, of Western Illinois University, also calls for scuba organizations to provide more training designed for polar conditions.
Interest in remote polar diving has grown as travel and diving equipment have improved. The review cautions that experience gained in temperate seas may leave important gaps because polar diving combines cold exposure with pressure, heavy equipment, limited access to the surface and a demanding environment where small errors can carry serious consequences.
Why polar diving places greater demands on the body
Water draws heat away from the human body far faster than air at the same temperature. A diver therefore loses heat even while wearing protective equipment, especially during long dives or periods with little movement. The face may remain exposed and hands can cool through gloves as they operate valves, clips, cameras and other equipment.
The body responds by trying to protect its inner organs and keep its core temperature stable. Blood vessels near the skin narrow, muscles may begin to shiver and energy use rises. A broad review of thermal stress describes these reactions as part of the body’s immediate defense against cold. The process can preserve heat for a time, although prolonged exposure may gradually overwhelm it.
Diving adds further strain because immersion changes how blood is distributed through the body. Breathing equipment creates resistance, while thick suits and added weights increase the work required to move. A polar diver may be managing cold, physical effort and a complex dive plan at the same time.
Cold shock can disrupt breathing within seconds
Cold water touching the face or entering a suit can trigger the cold shock response. The first moments may bring an involuntary gasp, followed by faster breathing and a strong sense of alarm. Even a trained diver can briefly struggle to regain a steady breathing rhythm.
Hyperventilation, or breathing much faster and deeper than needed, can make careful equipment use more difficult. It may also increase air consumption, shorten the planned dive and add to feelings of panic. A diver who enters the water too quickly or discovers a leaking seal may face several of these problems together.
According to the paper’s abstract, “Changes in both physiological and behavioral functions may occur quickly in these types of environments.” The speed of the response makes preparation at the surface especially important. Regulators, masks, suit seals and buoyancy controls need to be checked before the diver enters the water, when corrections are easier to make.
How near-freezing water affects the heart
Near-freezing water activates the body’s automatic stress systems. Heart rate may rise during the first cold exposure, while blood vessels in the arms and legs tighten to reduce heat loss. Known as peripheral vasoconstriction, this reaction sends more blood toward the chest and central organs.
Immersion itself also shifts blood inward because water pressure presses against the legs and lower body. Cold and immersion can therefore place overlapping demands on circulation. The exact response varies with fitness, health, suit protection, water temperature and the intensity of the dive.
Rapid breathing and an elevated heart rate can increase a diver’s sense of stress at the start of a descent. Slow entry procedures and time to settle at the surface may help the diver establish control before moving deeper, provided local conditions and the dive plan allow it.
People with heart or circulation problems may face greater risk during extreme cold exposure. Medical screening for diving should account for the planned environment because a person who tolerates easy dives in mild water may respond differently in polar seas.
Falling hand temperature weakens control
Hands are among the first body parts to lose useful warmth. The body reduces blood flow to the fingers as it tries to conserve core heat, while cold water continues to draw energy through gloves. Thick gloves can slow cooling, although their bulk may also make small controls harder to operate.
Manual dexterity begins to decline as skin and muscle temperature fall. Fingers may feel stiff or numb, grip strength can weaken and simple actions can take longer. Tasks such as securing a hose, adjusting a buckle, reading a small display, or sharing air require reliable hand control.
Cold also reduces the ability to feel pressure against the skin. A diver may have trouble judging whether a clip is fully closed or whether a control has moved into the correct position. Repeated attempts consume time and breathing gas and frustration can increase the diver’s mental load.
Equipment selection should account for real glove thickness and the conditions expected at the site. Practice sessions in controlled cold water can reveal whether valves, inflator buttons, release clips and emergency systems remain usable before the diver reaches a remote polar location.
Thermal stress can cloud decisions underwater
Cooling affects more than muscles. As discomfort grows, attention may narrow toward the feeling of cold, leaving fewer mental resources for navigation, depth control, gas checks and communication with a partner. The diver may process information more slowly or miss a change in the surroundings.
Thermal stress can also influence mood and risk assessment. A person who feels pressure to complete a planned route may delay ending the dive, even as hand control and concentration decline. Fatigue can further reduce the ability to solve an unexpected problem.
A separate 2026 deep-diving study involving three Italian Navy divers found signs of temporary cognitive change after a demanding dive to 89 meters. Its tiny sample and different environment limit comparisons with recreational polar diving, although the findings add to evidence that demanding underwater conditions can affect mental performance.
Good situational awareness depends on regularly checking the diver, the partner and the environment. Teams can use simple signals and agreed turning points so that ending a dive does not depend on a long underwater discussion after cold stress has already developed.
Why warm-water experience may create false confidence
Thousands of dives in tropical or temperate water can build strong skills, yet the same experience may encourage a diver to expect familiar physical responses. Polar water changes the time available for equipment work, problem solving and recovery from a mistake.
A warm-water diver may also judge personal cold tolerance from surface activities. Swimming in cold water, standing in winter air and working underwater while breathing compressed gas place different demands on the body. Diving equipment can hide early cooling while still allowing the hands and face to become stressed.
The review’s research summary highlights the risk that experienced warm-water divers may overestimate their ability to manage near-freezing conditions. Familiarity with scuba procedures remains valuable, while polar competence also requires direct preparation for cold exposure.
Conservative plans can account for the learning curve. Shorter initial dives give teams a chance to evaluate suit insulation, hand function, breathing rate and comfort. Divers can then adjust later plans according to observed performance rather than confidence alone.
Dry suits cannot remove every cold risk
A dry suit creates a waterproof layer around most of the body and allows insulating clothing to be worn underneath. Its protection depends on the suit, the undergarments, the fit, the diver’s activity level and the length of exposure. Water leaking through a neck or wrist seal can quickly increase heat loss.
Insulation also compresses as pressure rises during descent. Divers add gas to the suit to reduce squeezing and maintain an insulating space, which introduces another buoyancy control task. Gas movement inside the suit can affect body position, particularly when a diver is inexperienced with the equipment.
Hands and the head may still cool even when the torso remains relatively comfortable. Cold breathing gas and contact with metal equipment can add discomfort. A diver may therefore feel generally protected while finger control is already declining.
Layering must be matched to water temperature and planned activity. Too little insulation speeds cooling, while excessive bulk can restrict movement and require additional weight. Familiarity with the complete system, including emergency procedures, is essential before entering an overhead ice environment.
Polar divers need environment-specific training
Environment-specific training can prepare divers for problems that appear less often in warmer water. Useful practice includes managing a sudden suit leak, operating equipment with thick gloves, responding to rapid breathing and recognizing when cold is reducing a partner’s abilities.
Polar diving may also involve ice overhead, restricted entry points, surface support and long travel times to medical help. Training programs should connect thermal safety with the actual dive setting, including clear limits for water time and procedures for warming after surfacing.
The review urges scuba training organizations to include more information about extreme cold in their educational programs. Its recommendations come from a review of known physiological and behavioral responses rather than a large clinical trial, so many details still depend on the individual diver and the conditions of each dive.
Teams can reduce risk through careful planning, appropriate equipment, conservative exposure limits and honest communication about discomfort. Early signs such as uncontrolled breathing, loss of finger control, confusion, or persistent shivering provide reasons to follow the agreed exit plan.
As tourism and scientific access bring more people to polar seas, training standards will need to keep pace. Knowledge of cold water immersion gives divers a clearer basis for deciding when to continue, when to shorten a dive and when to leave the water before cooling weakens their ability to act.
