Every Friday, the Roctopus ecoTrust meets up at Victor’s Bar on Sairee Beach at 5:45 pm for a weekly beach clean‑up. Every Saturday, the team heads out for clean‑up dives around the island, pulling up debris that could otherwise damage the reefs you come here to dive on. Led by marine biologist Matt Knott, dive masters in training (DMTs) and volunteers join in – not just to clean up the ocean, but also to collect important long‑term data that gets sent to global projects like Clean Swell. The numbers show far more than ‘we cleaned a lot this week’; they reveal where Koh Tao’s pollution really comes from and how it changes once you move from the beach down to the reef.

Unveiling pollution patterns

Since November 2022, the team has organised 235 beach clean-ups, removing 49,618 items estimated at 4,500 kg (9,900 lbs). Clean-up dives began in November 2024, with 54 completed at 11 reef sites, including Aow Leuk, Hin Wong Bay, Buddha Point, and Tao Tong, collecting 15,823 items weighing roughly 2,000 kg (4,400 lbs). The figures are based on activities conducted through early April 2026, with both the weekly beach clean‑ups and clean‑up dives still ongoing, so these numbers will continue to grow. 

When you line these datasets up over months and years, clear patterns start to emerge. On the beach, nearly 37% of all items are linked to smoking, which makes it by far the most common debris category (see Figure 1, left). Plastics from drinks (bottles, cups, lids) and food‑related items also appear in large numbers, together accounting for around 16–17% of the beach haul, while miscellaneous and marine‑related items make up another big chunk, each around 10–12%. Averaged across sessions, cigarette butts stand out as the heaviest offender, with around 82 found per beach clean‑up, far ahead of everything else (see Figure 2, light green). Large plastic pieces such as plastic bags, food packaging, and plastic fragments also appear in large numbers, showing that both single‑use plastics and broken plastic waste are a constant problem on Koh Tao’s shores. 

Underwater, the story shifts. Clean‑up dives show that plastic beverage items dominate, making up over a third (34.9%) of all debris collected (see Figure 1, right), with food- and marine-related item categories each contributing around 13%. Packaging, apparel, and miscellaneous items are also common, while smoking‑related debris is almost absent underwater. This suggests that most cigarette waste either stays on the beach or gets buried in the sand and sediment, where it’s harder to spot. There, it can still cause serious damage to marine life as it slowly breaks down, leaching toxins into the surrounding environment. Averaged per dive (see Figure 2, dark green), the most striking items are plastic bottles (around 115 per dive), lines, nets, and ropes (around 62 per dive), and food‑related rubbish like food wrappers and containers (averaging 38 and 4–5 per dive, respectively). These consistently high averages mean that even a single clean‑up dive can remove a shocking amount of heavy, long‑lasting debris from the reef, particularly plastic bags, apparel, and other persistent plastic waste that would cause damage to the reef otherwise. 

The data clearly shows that smoking and plastic drink containers are the biggest issues on the beach, while plastic drinks, food packaging, and fishing‑related items are the main problems on the reef. This provides a useful snapshot of exactly where to focus education and behaviour‑change efforts on Koh Tao, as illustrated in both Figure 1 (share‑by‑category pies) and Figure 2 (average‑items‑per‑session bars). That tells us that while tourism brings visible surface litter, local fishing and everyday island consumption are quietly feeding the reef with persistent, long‑lived debris.

Each pie represents all items collected in each activity; each slice represents a category (food-related items, plastic beverages, etc.), sized by total item count and as a percentage of the total. This makes it easy to see which category dominates each activity.

Each bar is the average number of items per clean‑up (beach or dive) for a given category, with error bars showing the standard error. This highlights which items are consistently heavy offenders (e.g., plastic bottles underwater, cigarette butts on the beach) and how much variation there is from session to session.

The hidden impact of weekly clean‑ups 

At first glance, a weekly beach clean‑up might seem like a small gesture, but the Roctopus ecoTrust’s long‑term data shows that repetition is exactly what makes these actions powerful. By logging the total amount of rubbish collected each week and cataloguing the items, we can see how much interference we’re removing from the ecosystem before it reaches the reef. Marine debris often starts on the sand, then gets carried by waves and currents into shallow bays and coves, where it can settle on reefs and smother coral or entangle reef life. Removing that debris before it moves offshore is a core aim of the weekly beach cleans.

The weekly clean‑up dives do the same underwater, targeting the debris that’s already snagged on the reef: plastic bags, nets, and fishing line that can cause mechanical damage to coral structures or block light from polyps, severely affecting their survival. The data from these dives helps us understand how much debris is being removed from key sites and which items keep showing up most often, giving the Roctopus ecoTrust valuable insight into where and how often intervention is needed. In this way, conservation isn’t about one big ‘hero’ dive; it’s about the steady, logged, and measurable work that builds up over time.

From divers to data scientists 

Diving with a purpose changes how you see the underwater world, and it also changes how you see yourself. During beach cleans and marine debris dives, every piece of rubbish isn’t just something to be bagged; it’s an entry in a dataset. We record the type of each item, its material, and the location and characteristics of the collection site, then submit this information to Ocean Conservancy’s Clean Swell platform. That means our local work on Koh Tao is feeding into global marine‑debris research and policy, helping to identify hotspots and high‑risk materials.

At the Roctopus ecoTrust, the weekly clean‑up dives turn into long‑term science. Instead of stopping at the clean‑up, DMTs and volunteers systematically categorise the debris they collect, comparing what turns up at different dive sites and during different seasons. This approach turns divers into citizen scientists: they’re not just cleaning; they’re monitoring what kinds of debris are most likely to influence reef ecosystems and under what conditions. When the data shows that certain types of plastic or fishing gear repeatedly appear in the same areas, it highlights where education, policy changes, or stricter waste controls might be most effective. In this way, every diver who joins a clean‑up dive or beach session is contributing to a long‑term, evidence‑based strategy for protecting Koh Tao’s reefs.

What your vacation leaves behind 

The numbers from Roctopus ecoTrust’s clean-up activities tell an honest story about tourism: many of the most common items we pull from beaches and reefs are directly linked to visitors’ daily habits. Plastic water bottles, snack wrappers, takeaway containers, and cigarette butts show up again and again in the data. The records also show that some of the most damaging debris, like derelict fishing gear, often comes from local fishing and boating activities around the island, which can indirectly affect the same reef areas that tourists visit and enjoy.

But this isn’t about pointing fingers; it’s about turning awareness into real change – and for everyone to be part of that change. Small changes can make a big difference: cutting down on single‑use plastics, switching to reusable bottles and bags, recycling properly, using ashtrays, avoiding litter, and getting involved in local clean‑up activities. The message is simple: every single-use item you refuse and every piece of trash you remove is a small but measurable step toward a healthier reef. The Roctopus ecoTrust’s long‑term datasets show that protecting Koh Tao’s marine life isn’t about one big overhaul; it’s about thousands of small, conscious choices – choices that you can make every day.

By: Stef Meliss, ecoDivemaster