Divers Overestimate Their Skills and beat up reefs

Research at the University of Sydney has found that scuba tourism -- widely promoted as a sustainable way to experience coral reefs -- is causing frequent and often hidden damage to fragile marine ecosystems.

The study, led by Dr. Bing Lin from the University of Sydney's School of Geosciences, analyzed the behavior of more than 700 scuba divers in the Philippines and Indonesia.

From more than 300 hours of underwater observation, the researchers recorded 4,981 reef contacts by 411 divers. Around 41 percent of these contacts caused observable coral damage, from breakage to the stirring of sediment that can smother reef life.

On average, divers made roughly one contact every four minutes -- and spent nearly two seconds of every minute in direct contact with the reef.

Most damage is not deliberate. More than 80 percent of damaging contacts were unintentional or unnoticed by the diver, revealing how routine tourism activity can quietly degrade reef systems. Further, most divers in the study self-reported very high pro-environmental attitudes, suggesting that they care about reef conservation.

Overconfidence and Psychological Biases in Divers

The study also uncovered several striking psychological patterns. First, around three-quarters of divers rated themselves as "above average" in their ability to avoid reef contact compared to their peers -- an example of the illusory superiority effect, wherein people systematically overestimate their abilities relative to others.

Additionally, the study also documented that divers with lower skill levels disproportionately overestimated their competence.

"Many divers believe they are careful and low impact, but our data shows a consistent mismatch between perception and behavior," Dr. Lin said. Divers underestimated how often they contacted the reef by nearly fivefold.

Divers using cameras, gloves, or pointer sticks had higher contact rates, while peer behavior also played a significant role -- when one diver touched the reef, others were much more likely to follow suit.

Wildlife Encounters Worsen Reef Impacts

The presence of marine animals increased intentional reef contacts by 220 percent, unintentional contacts by 85 percent, and damaging contacts by 106 percent, often as divers approached or adjusted their position to observe the wildlife.

Dr. Lin said. "Unregulated underwater tourism is an overlooked local driver of damage that adds to, and amplifies, other acute and chronic reef stressors."

With coral reefs already under pressure from climate change, pollution, and overfishing, the findings highlight the need to better manage tourism impacts in heavily visited regions.

Training and Industry Standards as Solutions

Yet, a small minority of divers accounted for a disproportionate share of reef damage, suggesting practical solutions -- improved buoyancy training, stricter controls on equipment use, stronger environmental briefings, and higher standards in diver and dive-operator certification -- to reduce cumulative damage.

"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," said Lin.

This is from an article by Sadie Harley and Robert Egan at the University of Sydney. The study, Causes and Correlates of Unsustainable Scuba Diving Tourism on Coral Reefs, can be found in Conservation Letters (2026). DOI: 10.1111/con4.70055