Most plastic does not start in the Ocean. It travels. Rain lifts fragments and packaging from sealed streets; rivers concentrate them; waves and wind re-suspend them along coastal areas. Some waste is lost directly in the sea. This article explains the main pathways through which plastic enters marine environments, clarifies the mechanisms that move it, and indicates where interception is most effective for marine pollution control. Leakage is the outcome of deficient end-of-life and discards along logistics; the driver is mismanaged flows; verified end-of-life and targeted interception break the chain.

Urban runoff

In cities, impermeable surfaces behave like conveyors. During rainfall, buoyant items (such as lightweight packaging) and dense fragments are mobilised by sheet flow and street gutters. Road dust contains microplastics generated by tyre and brake abrasion; when the first flush arrives, these particles detach, suspend, and move into storm drains. In some cities, rainwater pipes and sewage pipes are connected (combined systems). When heavy rain exceeds their capacity, the mix of rain and wastewater flows directly into rivers or the sea. The main process is that rainwater picks up and carries plastics into drains and channels; once they reach open streams, they move quickly and can travel far without being held back.

Rivers as conveyors

Rivers act like long conveyors. They collect inputs from urban runoff, wastewater outfalls, industrial estates, open dumps along floodplains, and accidental losses during transport. Floating waste often gathers in lines in bends; light films drift under wood; heavier pieces sink and can be lifted again when the flow increases. Estuaries add another step: calm tides let plastics settle on mud, while ebb tides push them out to sea. In short, once plastic enters a river that flows all year, the chance it reaches the sea grows with stronger floods, steep slopes, and shorter distance to the coast.

Coastal re-suspension

Along coastal areas, waves and wind keep moving litter that was left on the shore. When plastics dry, they get lighter and the wind can blow them back to the water. Storm waves dig into the sand and uncover buried plastics, sending them drifting again. Near the coast, waves and currents trap items for a while, then rip currents carry them back out to sea. Small pieces often gather with seaweed on the beach, where they break down further under sunlight and rubbing. This means beaches are not just places where plastics stop, but can also release them back into the sea.

Maritime sources

At sea, losses occur from multiple activities. Navigation and cargo handling can release plastic packaging during rough weather. Fishing operations contribute via gear wear and accidental loss; when nets or lines are cut or abandoned—ghost gear (derelict fishing gear that continues to fish)—they drift or sink, entangling fauna and abrading into fragments. Aquaculture platforms also shed ropes and floats under wave stress. Shipboard waste management gaps, particularly on smaller vessels, add intermittent leakage when storage capacity is exceeded or segregation fails. This happens when equipment breaks or rubs against itself, cutting or wearing down plastics, or when storage systems fail and items escape during normal operations.

Extreme events

Floods, storm surges, and landslides act like sudden bursts. They wash away waste from open dumps, riverbanks, and damaged storage sites. In deltas, high waters pick up city litter and push it back and forth between land and sea; when waters go down, plastics keep flowing out for days. After wildfires, with less vegetation, rain runs off faster and carries plastics trapped in soil straight to rivers. These extreme events can release in hours what would normally leak over years.

Interception works best when it focuses on how plastics actually move. In cities, the most effective points are just before, during, and right after heavy rain: simple traps at drains, screens on busy channels, or nets in underground pipes that can be cleaned regularly. All captured waste must then be sent to verified recycling or safe disposal. On rivers, floating booms placed above tidal zones can catch plastics on the surface without stopping boats. In estuaries, barriers in calm side channels help skim debris without picking up too much driftwood. On beaches, clean-ups right after storms remove large items that waves have uncovered before they break into smaller pieces.

In the sea, recovery integrates with daily operations. The Fishing for Litter model recruits working boats to retrieve debris encountered during normal activity, with safe storage on board and controlled delivery in port. Ghost gear removal combines diver surveys on known snag grounds with safe lifting protocols. Across these contexts, the driver of credibility is traceability: each collection must be logged, weighed, categorised, and assigned an end-of-life route that prioritises recycling when feasible.

Ogyre is the first global platform based on the Fishing for Litter model, committed to recovering litter through a network of local waste fishers active in Italy, Brazil, Indonesia, and Senegal. We operate both at sea—collecting debris directly from water—and along coastlines, intercepting ocean-bound waste before it reaches marine environments. Our work supports the entire recovery chain: we provide logistical and financial assistance to those involved in collection, from fishers to local partners managing the end-of-life of recovered materials. Everything collected is delivered to certified cooperatives that ensure proper sorting, recycling, or responsible disposal—always aiming for the most sustainable outcome. Each activity is tracked through blockchain technology to guarantee full transparency, traceability, and data integrity. This approach transforms plastic and waste into shared value, engaging people, communities, and businesses in a circular model for protecting the Ocean.

Plastic reaches the sea because flows are mobilised and connected: runoff to channels, channels to estuaries, estuaries to the nearshore, and losses at sea. The levers are equally clear: intercept the flow where transport is concentrated; time operations to hydrological and oceanographic pulses; and verify end-of-life to avoid re-entry. Once pathways are mapped, prevention and recovery become operational, not aspirational.

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👉 How big is global plastic waste today? link

👉 How does mismanagement fuel marine pollution? link

👉 What is marine litter made of? link

👉 How to classify micro and macroplastics? link

👉 Floating vs. seabed plastic: which is worse? link