What do old televisions, street signs, motorbike helmets, windsurf boards, and Christmas trees have in common? They were all caught floating down Amsterdam's Westerdok canal -- by a curtain of bubbles.

"The Bubble Barrier" was developed as a simple way to stop plastic pollution flowing from waterways into the ocean. An air compressor sends air through a perforated tube running diagonally across the bottom of the canal, creating a stream of bubbles that traps waste and guides it to a catchment system.

It traps 86% of the trash that would otherwise flow to the River IJ and further on to the North Sea, according to Philip Ehrhorn, co-founder and chief technology officer of The Great Bubble Barrier, the Dutch social enterprise behind the system.

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