New research reveals that scuba-diving tourism — long marketed as eco-friendly — is quietly degrading coral reefs, with most divers significantly underestimating how often they make harmful contact with fragile marine ecosystems.
Scuba diving is frequently sold as a low-impact way to experience coral reefs up close. But a new study published in Conservation Letters suggests the industry’s environmental footprint underwater is far larger than most divers — or operators — realize.
Researchers led by Bing Lin, a postdoctoral research associate at the University of Sydney’s Thriving Oceans Research Hub in the School of Geosciences, analyzed the behavior of more than 700 scuba divers across popular tourism sites in the Philippines and Indonesia, including Bali. Drawing on over 300 hours of underwater observation, they recorded nearly 5,000 reef contact events among 411 divers — and found that roughly 41%of those contacts caused observable damage, from snapped coral to sediment disturbance that can suffocate reef life.
On average, a diver made contact with the reef once every four minutes and spent close to two seconds of every minute physically touching it.
“This work documents the unsustainable underwater footprint of scuba diving tourism on coral reefs,” Lin, who began the research as a doctoral student at Princeton University and completed it as part of his postdoctoral position at the University of Sydney, said in a news release.
Most Damage Goes Unnoticed — Even by the Divers Causing It
Perhaps the most striking finding is how invisible the damage is to the people responsible for it. More than 80% of harmful contacts were either unintentional or completely unnoticed by the diver in the moment. At the same time, the majority of participants reported strong pro-environmental attitudes and said they genuinely cared about reef conservation.
That gap between good intentions and actual behavior is compounded by well-documented psychological biases. About three-quarters of divers rated themselves as better than average at avoiding reef contact — a textbook example of the illusory superiority effect.
The study also found evidence of the Dunning-Kruger effect, where less-skilled divers were the most likely to overestimate their abilities.
“Many divers believe they are careful and low impact, but our data shows a consistent mismatch between perception and behaviour,” Lin added.
In side-by-side comparisons of diver self-reports and observed behavior, divers underestimated their reef contact frequency by nearly fivefold.
Cameras, Wildlife Encounters and Peer Pressure Make Things Worse
The study pinpointed several behaviors that significantly drove up contact rates. Divers who brought underwater cameras, wore gloves, or carried pointer sticks were more likely to touch the reef. Social dynamics also played a measurable role: when one diver made contact, others in the group were much more likely to do the same.
Wildlife sightings — often the main draw of reef tourism — turned out to be especially damaging moments. The presence of marine animals increased intentional reef contacts by 220%, unintentional contacts by 85%, and damaging contacts by 106%, as divers repositioned themselves to get a better look or moved in closer.
The researchers also found that a small subset of divers was responsible for a disproportionately large share of the overall damage, which suggests that targeted interventions — focusing on high-impact individuals or specific behaviors — could go a long way.
“But what is clear is that unregulated underwater tourism is an overlooked local driver of damage that adds to, and amplifies, other acute and chronic reef stressors,” added Lin.
Why It Matters for Students and Travelers
For college students who travel, scuba dive, or are considering dive certification, these findings carry direct relevance. Reef tourism is a global industry, and many young travelers choose diving specifically because they believe it to be environmentally responsible. This research challenges that assumption and points toward what meaningful responsibility actually looks like.
“Tourism is critical to many coastal economies, including those closely linked to Australia,” Lin added. “But without changes to diver behaviour, training and industry standards, it risks undermining the very ecosystems it depends on.”
Coral reefs are already under severe pressure from climate change, pollution and overfishing — tourism adds yet another layer of stress that has largely flown under the radar.
The research team recommends a range of practical fixes: better buoyancy training before dives, tighter restrictions on equipment like cameras and gloves in sensitive areas, more rigorous environmental briefings, and higher certification standards for both divers and dive operators.
“First and foremost, divers need to understand that they are a part of the problem before we can convince them to become a part of the solution,” Lin added.
Source: University of Sydney