How Long Can Polar Bears Swim Underwater?

Polar bears are powerful swimmers, relying on their aquatic abilities to navigate the Arctic in search of food and suitable habitats. While not fully adapted to life underwater like marine mammals, they demonstrate impressive swimming and diving capabilities.

Physical Adaptations For Aquatic Life

Polar bears possess physiological and anatomical traits that enable them to navigate Arctic waters efficiently. Their elongated bodies and powerful forelimbs generate strong propulsion, allowing them to cover vast distances in search of ice floes and prey. Their large, slightly webbed paws function as natural paddles, increasing surface area and improving thrust while minimizing energy expenditure—critical for survival in an environment where prolonged swimming is often necessary.

Their fur, while primarily designed for insulation on land, also aids buoyancy. Each hollow hair shaft traps air, reducing overall density and helping the bear remain afloat. Beneath the fur, a thick layer of subcutaneous fat—ranging from 4 to 11 centimeters—provides additional buoyancy and insulation against frigid waters. This fat layer is especially pronounced in well-fed individuals, allowing them to endure extended periods in icy seas without succumbing to hypothermia.

Polar bears also exhibit physiological adaptations that support their aquatic lifestyle. Their nostrils close reflexively when submerged, preventing water intake. Additionally, their heart rate slows during dives, a response known as bradycardia, which conserves oxygen and prolongs submersion time. This mechanism, common among marine mammals, is particularly useful when navigating beneath ice or pursuing prey.

Underwater Durations

Polar bears generally remain underwater for 30 seconds to a minute while diving. Unlike seals or whales, which have specialized oxygen storage mechanisms for prolonged dives, polar bears rely on rapid, shallow submersions to navigate beneath ice or approach prey undetected. Their lung capacity is substantial for a terrestrial carnivore but does not match that of species evolved for deep-sea foraging.

While most dives are brief, some observations suggest they can extend submersion time under specific conditions. A 2014 study published in Polar Biology documented an adult polar bear swimming underwater for 72 seconds while chasing a seal—representing the upper limit of their known diving duration. Such extended submersions are likely facilitated by bradycardia, which slows the heart rate to conserve oxygen. However, these longer dives are rare and usually occur during high-stakes hunting attempts.

Temperature and exertion levels also influence how long a polar bear can stay submerged. Cold water increases metabolic demands, requiring a balance between oxygen conservation and thermoregulation. Unlike marine mammals with extensive adaptations for deep diving, polar bears must resurface frequently to replenish their oxygen supply. Their reliance on ice platforms and open breathing holes underscores their need for short, controlled dives rather than prolonged submersion.

Environmental And Behavioral Influences

The Arctic environment shapes how polar bears use their swimming and diving abilities. Seasonal ice coverage dictates access to hunting grounds, with summer months often requiring longer swims between fragmented ice floes. As sea ice diminishes due to rising global temperatures, these swims are becoming more frequent and prolonged, increasing physical demands and mortality risks, particularly for younger or weaker individuals.

Behavioral adaptations help mitigate these challenges. Polar bears often rest on floating ice between swimming bouts, conserving energy before resuming their journey. Mothers with cubs are especially strategic, choosing routes with the highest likelihood of encountering stable ice to reduce strain on their offspring. While adult bears are strong swimmers, cubs lack the same endurance and rely heavily on their mothers to navigate treacherous waters. Observations indicate that maternal strategies include frequent resurfacing and shorter dive durations to ensure cubs can follow without becoming fatigued.

Social and predatory behaviors also influence how polar bears interact with their aquatic surroundings. Opportunistic hunting tactics often keep them near ice edges where seals surface for air, minimizing the need for extended dives. When stalking prey in open water, they may use a combination of slow, deliberate movements and sudden bursts of speed to close the distance. Older, more proficient hunters demonstrate refined techniques that maximize success while conserving energy.

Diving For Prey

Polar bears rely on stealth, speed, and precise timing when diving to catch their primary prey—seals. Unlike marine mammals that dive to great depths in search of food, polar bears use relatively shallow submersions to gain a tactical advantage. Seals often rest on sea ice or surface at breathing holes, making them vulnerable to sudden underwater attacks. A bear approaching from a distance will often slide silently into the water, submerging just enough to remain hidden while closing the gap. This reduces the likelihood of detection, allowing the bear to launch an ambush from below.

When a seal is within striking range, the bear propels itself upward with a powerful kick of its hind legs, breaking through the water’s surface with enough force to seize its target before it can escape. This technique requires precise coordination, as any miscalculation may allow the seal to slip away. Young and inexperienced bears often struggle with timing these attacks, leading to unsuccessful hunts. Observations suggest that older individuals are more adept at using environmental features, such as ice formations, to funnel prey into confined spaces where escape routes are limited.