Unsightly scenes of rubbish floating in the water are sadly how many visitors recall their voyage around Vietnam's famous Ha Long Bay, which is famed for its emerald waters and towering limestone islands. While the UNESCO World Heritage Site remains a magical landscape, it faces many environmental challenges as it attracts more and more visitors. A pressing problem is that it's being polluted with litter, waste and discarded fuel from the boats that ferry visitors.

Before and after: how world-famous views could look if pollution continues unchecked

Vacation hot spots ruined by trash and tourism