How noisy is the underwater environment? Tom Heap dips beneath the surface to find out if man-made noise is affecting the marine life that lives below the waves.

Costing The Earth begins a new series with three programmes investigating the health of our oceans. The team tackles ocean acidification and how the UK plans to protect marine areas in its overseas territories but first Tom Heap delves into a mystery soundscape: one that exists underwater.

Scientists are only just beginning to study the complex noises coming from beneath the waves. All marine life depends on sound to communicate but in a world that is becoming increasingly loud, whales, dolphins, fish of all shapes and sizes, all the way down to molluscs and the smallest organisms are finding their voices lost in a sub-aqua world of rumbles and crunches from various man-made sources.

Presenter: Tom Heap
Producer: Martin Poyntz-Roberts.