It's difficult on a ship to get away from your job because that accommodation house, which is where seafarers live, is their workplace, it's where they live, it's where they relax, it's everything, and it's just hard to get away. And seafarers often refer to their job as being in prison with a salary.

I went down to the sewers in London and looked at a campaigning group in London called RATS, Rowers Against Thames Sewage, and I went to Sewage School and hung out with kids learning to make sewage soup and how to clean sewage. And it was great - really good fun.

The days of languorous shore leave are long gone. Overnight stays are unheard of and sailor towns a distant memory. In better ports, seafarers head for a seamen's mission.

We know about man's impact on the ocean in terms of fishing and overfishing, but we don't really know much about what's happening underneath the water. And in fact, shipping has a role to play here, because shipping noise has contributed to damaging the acoustic habitats of ocean creatures.