They Dive into Icy Seas Without Oxygen Tanks—Meet Korea’s Haenyeo Sea Women

On the windswept shores of South Korea’s Jeju Island, the Haenyeo of Jeju: fearless women divers, plunge into icy seas armed only with spears and grit, harvesting octopus, abalone, and seaweed. For over a millennium, these “sea women” have braved the cold without oxygen tanks.

In 2016, UNESCO inscribed the “Culture of Jeju Haenyeo (women divers)” on its Representative List of the Intangible Cultural Heritage of Humanity, recognizing their intergenerational, women-led cooperatives and ecological knowledge as a global treasure. ⁽⁴⁾ From approximately 14,000 in 1970, their numbers declined to ~4,500 by 2013 and 4,005 by 2015, with most active Haenyeo now in their sixties or older. ^(1,4)

Have you ever wondered how do Haenyeo work for hours in winter seas averaging 10–13 °C? The answer lies in the fact that their bodies execute a survival duet of reflex and acclimatization. In a field study of nine divers, all showed diving bradycardia: mean heart rates dropped by ~20 ± 8% at the bottom (≈101 ± 20 bpm) compared with surface swimming (≈125 ± 16 bpm), conserving oxygen for vital organs ⁽²⁾. Long-term cold exposure historically raised basal metabolic rates and lowered shivering thresholds; while wetsuits introduced in the mid-1970s reduced systemic cold stress, local cold tolerance in the face and hands remains notable, ^(1,2)

A 2025 study shows Jeju islanders form a distinct genetic cluster from mainland Koreans, diverging ~5,000–7,000 years ago. It identifies a variant (rs66930627) associated with lower diastolic blood pressure, and concludes that Haenyeo’s diving bradycardia is primarily training-driven, not genetic ⁽³⁾. Unlike the Bajau sea nomads, who have genetically larger spleens for oxygen storage, Jeju natives show no evidence of enlarged spleens; the two populations should not be conflated. ⁽⁷⁾

Even into their seventies, Haenyeo display remarkable resilience. In cold seas, they maintain performance through bradycardia and training-hardened routines. In a winter field study (mean daily exposure ~253 ± 73 min; water 10–13 °C), older divers among nine participants had shorter dive times, fewer dives per hour, and lower working heart rates—patterns reflecting voluntary workload adjustments as cardiovascular capacity declines. ⁽²⁾ Emerging evidence on orexin and irisin supports this age-tempered adaptability. ⁽⁵⁾

Neoprene wetsuits introduced in the 1970s reduced systemic cold strain, attenuating whole-body acclimatization traits like elevated basal metabolic rates, though local cold tolerance persists. ⁽¹⁾ Some cross-adaptation benefits likely remain: Haenyeo show improved heat tolerance and higher sweat rates compared with non-divers, suggesting cold exposure builds all-season endurance. ⁽¹⁾ Media reports have suggested lower stroke mortality on Jeju, but these claims lack robust epidemiological confirmation, and no genetic link has been demonstrated. ⁽⁶⁾

With fewer young recruits, the Haenyeo’s future is uncertain. Recent fieldwork shows fewer dives per hour and longer recovery periods, reflecting aging demographics and safety-conscious pacing ⁽²⁾. Their story: biology, culture, and tenacity unlocks insights into human limits in extreme environments.

References

1. Lee, Joo-Young, S. Y. Lee, H. C. Kim, et al. 2017. “Cold Adaptation, Aging, and Korean Women Divers Haenyeo.” Journal of Physiological Anthropology 36 (33). https://doi.org/10.1186/s40101-017-0146-6.

2. Lee, Joo-Young, H. C. Kim, S. Y. Lee, et al. 2016. “Diving Bradycardia of Elderly Korean Women Divers, Haenyeo, in Cold Seawater: A Field Report.” Industrial Health 54 (2): 183–190. https://doi.org/10.2486/indhealth.2015-0125.

3. Aguilar-Gómez, Diana, et al. 2025. “Genetic and Training Adaptations in the Haenyeo Divers of Jeju, Korea.” Cell Reports 44: 115577. https://pubmed.ncbi.nlm.nih.gov/.

4. UNESCO. 2016. “Culture of Jeju Haenyeo (Women Divers).” Representative List of the Intangible Cultural Heritage of Humanity. https://ich.unesco.org/en/RL/culture-of-jeju-haenyeo-women-divers-01068.

5. Lee, Inho, Dong-Ho Park, Joo-Young Lee, and Yoonjung Yoon. 2022. “The Acclimatization of Haenyeo to a Cold Environment and Occupational Characteristics Evaluated by Orexin and Irisin Levels.” Annals of Occupational and Environmental Medicine 34: e28. https://doi.org/10.35371/aoem.2022.34.e28.

6. OPB / NPR. 2025. “Why South Korea’s Haenyeo Women Divers Are Key to Understanding Human Adaptation.” News reporting on the 2025 study and historical practices. https://www.opb.org/ and https://www.npr.org/.

7. Ilardo, Melissa A., Ida Moltke, Thorfinn S. Korneliussen, et al. 2018. “Physiological and Genetic Adaptations to Diving in Sea Nomads.” Cell 173 (3): 569–580. https://doi.org/10.1016/j.cell.2018.03.054

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