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As one of the largest passenger ships in the the world, the Liberty of the Sea has the potential to create a lot of pollution.
That's where Environmental Officer, John Marshall, steps in.
Tasked with ensuring the ship meets its legal obligations to have a minimal impact of the High Seas, he advises on and monitors all of the waste generated by the 4,000 passengers and crew aboard - everything from toilets to wine corks.
In this video, Steve Read caught up with John aboard the Liberty of the Seas and discovered that he not only has powers over the Captain to act, but used to be a Royal Marine.
He's certainly not a man to mess with - meaning any kind of 'mess'.

→ Watch Steve's video diary of his cruise aboard the Liberty of the Seas
→ Book a cruise on the Liberty of the Seas