How generations of ocean living shaped remarkable diving abilities — and what scientists discovered in their DNA.
Imagine growing up surrounded by the ocean, learning the rhythms of tides, boats and fishing grounds. For generations, the sea has been central to the lives of many Sama-Bajau communities of Southeast Asia. But scientists have also uncovered something less visible: evidence that one Bajau population developed biological adaptations associated with breath-hold diving.
Do the Bajau really represent humans adapting to life underwater? Their story is extraordinary — but it is not about people who can breathe underwater. It is about culture, physiology and natural selection.
Featured image: AI-generated editorial illustration; it does not depict a photographed person or specific village.
Who Are the Bajau Sea Nomads?
The Sama-Bajau are diverse maritime peoples living in parts of Indonesia, Malaysia and the Philippines. Some families historically lived on boats, while others built settlements over shallow coastal water. Fishing, boatmaking, marine trade and detailed knowledge of the sea have shaped different communities in different ways.
Not every Bajau person is a diver, and not all Bajau communities still follow a nomadic lifestyle. Many families live in permanent villages or towns. Their culture is not a single unchanging tradition.
Maritime Origins, Migration and Community Diversity
The names Bajau, Sama-Bajau, Bajo and Bajau Laut refer to related but diverse populations, with names and identities varying by community and region. Their history includes maritime travel, trade, encounters with other island populations and genetic exchange across Southeast Asia. Genomic research on the Bajo helps illuminate this population history. It is more accurate to describe diverse related communities than one isolated tribe.
Historical and linguistic evidence suggests maritime traditions extending back centuries, possibly a millennium or more, but this is not a precise date for the origin of any particular community or genetic adaptation. Explore research on Bajo population history.
How Deep Can Bajau Divers Go — and How Long Can They Hold Their Breath?
Some experienced traditional Bajau freedivers perform demanding underwater work, collecting seafood and spearfishing without scuba tanks. A 2018 University of California, Berkeley report describes dives exceeding 70 meters (about 230 feet), but such exceptional accounts must not be mistaken for typical daily dives or abilities shared by an entire population.
Long breath-holds reported in popular stories — sometimes described as reaching 10 or 13 minutes — should likewise not be presented as scientifically established averages. Diving performance varies between individuals and situations. Breath-hold diving can lead to blackout and drowning, even among skilled divers.
Five Bajau Divers: What Researchers Actually Observed
How does the daily work of traditional divers compare with extraordinary breath-holding claims online? A 2011 observational study followed five male Bajau spearfishers in the Philippines using direct observations and depth-time recorders. They worked in the water for approximately two to nine hours per day and spent on average 60% of their working time submerged.
Their recorded dives lasted 28 seconds on average, with average surface intervals of 19 seconds, mainly at depths of five to seven meters (about 16–23 feet). These figures describe the five people studied, not all Bajau divers.
This distinction matters: direct research documents frequent, comparatively short working dives, while reports of 13-minute breath-holds refer to exceptional performances. The daily pattern is remarkable because of how often the divers return underwater throughout their working day.
Original 2011 observational study: Schagatay, Lodin-Sundström and Abrahamsson.
The Discovery: Why Do the Bajau Have Larger Spleens?
A landmark study led by Melissa Ilardo and published in Cell in 2018 compared Bajau participants from Jaya Bakti, Indonesia, with Saluan participants from a nearby community. Researchers used ultrasound measurements and genetic analysis. They found that the Bajau participants had spleens approximately 50% larger on average than the comparison group.
The spleen stores red blood cells. During breath-hold diving, it can contract, releasing oxygen-carrying cells into circulation. An enlarged spleen may therefore offer a larger reserve to draw upon during periods without breathing.
Crucially, the researchers found enlarged spleens even among Bajau participants who did not dive. That observation suggests that training alone could not explain the difference. It does not mean every Bajau person has an enlarged spleen, or that the 50% figure applies to every community.
Read the original Cell study and the UC Berkeley research report.
Did the Bajau Evolve to Live Underwater?
The researchers reported evidence of natural selection involving variants near or within genes including PDE10A, associated with spleen size, and BDKRB2, linked to the diving response. The results are an important example of how cultural practices and human evolution may interact.
These findings do not imply that the Bajau have become a separate species, developed gills, or can breathe underwater. They are human beings who rely on oxygen just as other people do. Nor do these genetic associations demonstrate that every identified variant directly causes superior diving performance.
What the Genetic Findings Do — and Do Not — Explain
The 2018 investigation discussed possible relationships between PDE10A, thyroid-hormone signaling and spleen size. Earlier animal findings helped researchers examine this mechanism but do not establish every step of the process in humans. BDKRB2 was examined in connection with vascular regulation and the diving response.
There is no single proven ‘diving gene’. Genetic variation, physical training, practical technique, experience and maritime culture can all matter. These findings should be understood within the communities studied, not generalized to every Bajau person.
What Happens Inside the Body During a Dive?
When humans immerse the face in water and hold their breath, the mammalian diving response can slow the heart rate and redirect blood flow toward vital organs. The spleen may also contract. This reflex exists in other humans, too; the Bajau research explores population-level differences in traits related to it.
As oxygen falls, loss of consciousness becomes a serious risk. These scientific findings are not an instruction to practice long breath-holds underwater.
Do Bajau Children Have Special Underwater Vision?
Another famous underwater-vision study is often confused with the Bajau research. Researchers documented superior underwater vision among Moken children, members of a different Southeast Asian maritime population. Subsequent experiments showed that children from Europe could also improve underwater vision with training.
The Moken and Bajau are distinct peoples; findings about one should not automatically be attributed to the other. See the 2003 Moken study and 2006 training study.
A Culture Shaped by the Sea
Across different communities, maritime knowledge includes tides, currents, boats, fishing locations and the behavior of marine species. Stilt houses, wooden vessels and fishing traditions reflect the ocean’s influence on daily life. But Bajau families also engage with schools, technology, wage employment and changing regional economies.
Why Is the Traditional Way of Life Changing?
For some sea-oriented communities, access to schooling, citizenship documentation, coastal development, fishing resources and environmental change are significant concerns. Experiences differ by location: it would be misleading to portray every Bajau community as facing the same challenges or as living outside modern society.
Their future should not be framed simply as preserving a lifestyle frozen in time. It is also about opportunities, rights and the ability to maintain cultural traditions while communities themselves shape what comes next.
What Can the Bajau Teach Scientists About Human Evolution?
The Bajau study offers a valuable opportunity to investigate how humans respond to temporary oxygen shortage, or hypoxia. That may inform further research into physiology and genetics, but it has not established a medical treatment for hypoxia or shown that Bajau divers are immune to oxygen deprivation.
The Bajau did not become creatures of the sea. Their history instead shows how culture and human biology can change together across generations.
What This Story Teaches Us About Evidence and Extraordinary Claims
When investigating the Bajau, it is easy to see how a fascinating scientific story can become exaggerated when different kinds of evidence are confused. There are accounts of exceptional breath-holds, direct observations of working divers, and genetic and physiological studies. All are valuable, but they are not interchangeable.
An exceptional individual’s achievement does not describe an entire population. Evidence of natural selection does not make the Bajau biologically aquatic. The nickname ‘aquatic humans’ can attract curiosity, but it should not eclipse the communities’ histories, cultures and diversity.
The reality remains extraordinary even when the exaggeration is removed. Science does not need to transform the Bajau into a myth to explain remarkable human adaptation.
Frequently Asked Questions
Where do Bajau people live?
Sama-Bajau communities live in parts of Southeast Asia, including Indonesia, Malaysia and the Philippines.
Can the Bajau breathe underwater?
No. Bajau divers hold their breath; they cannot extract oxygen from water.
Why are Bajau spleens larger?
A study of one Indonesian Bajau community identified evidence of natural selection associated with larger spleen size, which may aid breath-hold diving.
Can Bajau divers hold their breath for 13 minutes?
Exceptionally long breath-holds have been reported, but 13 minutes is not a documented population average.
Do all Bajau still live on boats?
No. Sama-Bajau communities have diverse lifestyles, including permanent coastal and inland settlements.
Watch the Research on YouTube
Melissa Ilardo explains the scientific findings in a video featured by UC Berkeley. The research video is presented below with its institutional source.
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Scientific Sources and Image Credits
- Ilardo et al. (2018), Cell — Physiological and Genetic Adaptations to Diving in Sea Nomads
- UC Berkeley — Enlarged spleen key to diving endurance of sea nomads
- Gislén et al. (2003) — Superior Underwater Vision in a Human Population of Sea Gypsies
- Gislén et al. (2006) — Visual Training Improves Underwater Vision in Children
- Schagatay et al. (2011) — Observational study of Bajau and Ama diving
- Genomic and population history of the Bajo — PubMed Central
- National Geographic — Bajau diving and spleen research
- Photographs credited above: Benoît Vicart (CC0 1.0) and Torben Venning (CC BY 2.0), via Wikimedia Commons.
Editorial note: Physiological findings relate to the populations studied and should not be generalized to all Sama-Bajau people. Documentary photographs are identified and credited; the featured artwork is an AI-generated illustration.