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The study, published in , and in which ����VR��Ƶ marine scientist Dr Ronan Roche played a key role, analysed the behaviour of more than 700 scuba divers across tourism hotspots in the Philippines and Indonesia, including Bali.  

Drawing on data from more than 300 hours of underwater observation, the researchers, led by Dr Bing Lin from the University of Sydney, recorded 4981 reef contact events among 411 divers.  

Around 41% of these contacts caused observable damage to coral, from direct breakage to the stirring of sediment that can smother reef life. On average, divers made 0.26 reef contacts a minute – roughly one every four minutes – and spent nearly two seconds of every minute in direct contact with the reef. 

The study built on Dr Ronan Roche’s 2016 paper, published  journal, that focused on assessing the effectiveness of Green Fins, the largest global program to reduce scuba diving impacts on coral reefs.  

Dr Ronan Roche, Lecturer at Bangor University’s School of Ocean Sciences, who helped develop the methodology for the fieldwork in Indonesia and the Philippines, and later worked on the interpretation of the dataset and writing of the paper said, “This dataset allows us to understand the drivers of reef damage caused by scuba diving tourists to reefs with unprecedented levels of confidence. It shows that damaging contacts by divers with reefs were frequent, but mostly unintentional, and finds that the Green Fins program can be effective in reducing contacts made. 

“Global climate change is the dominant pressure on coral reefs, but reducing localised pressures on coral reefs is increasingly important. Reef managers can’t reduce sea temperatures, but they can control local pressures such as scuba diving, and this helps corals to recover and reproduce following damaging coral bleaching events. Ultimately this research aims to help find sustainable solutions to reef tourism that benefit both coral reefs and the communities that depend on them.” 

Dr Lin, who started the research during his PhD at Princeton University, completing it as part of his postdoctoral position at the University of Sydney said, “This work documents the unsustainable underwater footprint of scuba diving tourism on coral reefs,”  

A central finding of the study is that most damage is not deliberate. More than 80% of damaging contacts were unintentional or unnoticed by the diver, revealing how routine tourism activity can quietly degrade reef systems over time. In fact most divers in the study self-reported very high pro-environmental attitudes, suggesting that they by and large care about reef conservation.  

The study also uncovered several striking psychological patterns. Including overconfidence and psychological biases in divers 

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, where people systematically overestimate their abilities relative to others.   

Additionally, the study also documented the well-known Dunning-Kruger effect in divers, where people with lower skill levels disproportionately overestimated their competence.  

This overconfidence translated into a major gap between perception and reality. In matched observations, divers underestimated how often they contacted the reef by nearly fivefold.  

“Many divers believe they are careful and low impact, but our data shows a consistent mismatch between perception and behaviour,” Dr Lin said.  

The research identified several factors that were associated with increases in reef damage.  

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

Wildlife encounters – often the highlight of dive tourism – were found to significantly amplify damage. The presence of marine animals increased intentional reef contacts by 220%, unintentional contacts by 85%, and damaging contacts by 106%, often as divers approached or adjusted position to observe the wildlife.  

The study also found that a small minority of divers accounted for a disproportionate share of total reef damage, suggesting targeted interventions could have considerable benefits.  

“It’s difficult to quantify the true scale of the reef contact problem,” Dr Lin said. “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.”