Marine Debris

Materials: Plastics, Metal, and Wood, oh my!

The MATERIAL state of COASST marine debris describes the stuff an object is made of. Material properties can tell us about potential environmental impact (including how quickly objects degrade and how easily they are consumed in the marine environment) and source (because material can indicate an object’s relative buoyancy in the water, and the distance it might travel as a result).

This picture shows a slew of different material examples, Metal, Plastic (Hard, Foam and Soft), Glass, and Paper

COASST has 10 material category ‘bins’ that all marine debris can fit into: Plastic, Glass, Metal, Wood/Bamboo, Paper/Cardboard, Rubber, Cement/Ceramic, Other, Multi, and Unknown.

Generally we classify material with the predominance (or >50%) rule. If an object is made up of at least 50% one material, we lump it in that category.

The photos below should help provide some guidance for those times when the material is clear, but the COASST category isn’t.


Plastic is long-lasting (it is not biodegradable) and is COASST’s most common material.

The environmental impact tied to a piece of plastic debris is closely associated with the type of plastic, so we divide our plastic debris into three categories: Hard, Foam and Soft.

Hard Plastic: Hard plastic isn’t very flexible – if bent it either breaks into pieces or assumes its previous shape when pressure is lifted. Containers fall into this category because they are rigid items that can trap and transport animals. Common examples of Hard Plastic include water bottles, mooring buoys, drink cups, buckets, and nurdles.

Foam plastic: Foam goes by many names, including polystyrene, insulation, and styrofoam. Foam easily fragments – and may be classified as crumbly as it ages – resulting in many small pieces scattered throughout the wrack or wood zones. Foam can also harbor smell, which may be why we often see beak marks in it where birds have attempted to find their next meal.

Soft Plastic: Soft plastic is very flexible, and doesn’t hold its shape without support. Think of food wrappers, shopping bags, plastic film, and ropes. There are many specific names for these materials, including nylon, polypropylene, and mylar, as well as the materials that make synthetic clothing like fleece and spandex. Soft plastic characterized as floppy/loopy is an entanglement risk.


Often found as bottles or broken fragments, this material can be sharp (hazardous to wildlife and humans) if recently broken.


Metal makes up rigid materials, and when new is often shiny. Rusting and fragmented metal can be very sharp (hazardous to marine animals and humans).


Wood is the material most commonly reported for dimensional lumber on large debris surveys, but it can also make up furniture or small objects like chopsticks.

Reminder – firewood and driftwood do NOT count as marine debris. Though they are made of woody materials, those pieces of wood are not crafted or heavily modified by human hands.


These materials are often thin, floppy and at least partially biodegradable in the marine environment. We don’t see a lot of paper products reported because they degrade rapidly or blow away!


This material may be often seen in tires, bumpers, balls and rubber bands. The texture is elastic and bouncy!


The cement/ceramic category includes brick, conglomerate, and pottery – items that are non-metallic and stone-like after they are formed and dried or baked.


This state contains items that don’t fit into one of the above categories, but are a known/identifiable material, including non-synthetic cotton or wool clothing. When you mark ‘other’ material, you can also use the comment section to specify the type!


Sometimes an object is made up of many parts, and no single material makes up the majority. When that happens, you can select Multi and make sure to list the material categories that are present in the comments.


Sometimes a material is unrecognizable, or unfamiliar. Mark Unknown in this case, and put any guesses or details in the comments! (Did it have a smell? Was it rigid?)

Have you found a mystery material? Send an email with photos to COASST for review and second opinions. We will add images to this post as new examples pop up in the dataset!

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