Did you know that Cozumel, off Cancun, welcomes 24,000 cruise visitors a day to an island smaller than the Isle of Wight? Or that cruise and ferry ships emit a higher level of sulphur than power stations?

If you sell cruises and you did not know, a new web-based training course launched by the Association of Cruise Experts (Ace) and The Travel Foundation could be for you.

Make Cruise Greener is modelled on the Make Travel Greener training launched by The Travel Foundation in 2009.

Cruise and ferry ships are by no means the biggest contributors to global warming – cargo shipping is worse – but there is a pollution problem because cruises focus on a limited number of coastal areas and repeatedly visit the same ports.

Another problem is water pollution involving grey water from showers and kitchens and black water from toilets. A seven to 10-day cruise produces more than one million gallons of grey water that on some ships is just pumped overboard, and up to 21,000 gallons of black water a day.

The Make Cruise Greener training outlines these concerns and aims to make cruising more sustainable, with advice on answering customer queries. It suggests cruise passengers are encouraged to make more of destinations through language lessons and talks on local culture and food.

The four modules take about 30 minutes to complete, but allow you to break off, save what you have done and go back later.

Ace director Flo Powell said: “I would urge anyone working in the field to take this training. It was created specifically to help address consumers’ questions.”