aus005 said..
might be worth a look at 8.30 it is cruising on the windsurf sailing cruise ship

It was rubbish. Sails were for decoration. No one is going to believe they ever shut down the diesel electric propulsion. The under water shot showed a flat shallow bottom yet the sails were nearly always set for close hauled sailing. Driving with the diesel electric and using the sails to utilize the relative wind as a stabilizer I can believe. The diesels would be running all the time to power the air conditioning etc anyway.

I saw it too. The narrator said that under sails alone the ship can do 12 knots!
I tried to confirm that speed via some internet searches but I couldn't find any technical data.
12 knots is hard to believe.