Extinction Rebellion spokesman James Cockle said environmental groups the Red Rebels and Extinction Rebellion hosted a "wake" yesterday from 8am to 11am in the Octagon.
The protest featured signs made to resemble tombstones with the name and picture of animals and birds that went extinct in living memory.
The group were there to bring attention to the damage cruise ships have on the environment and were passing out flyers to cruise ship passengers and members of the public.
The protest coincided with the arrival of about 2600 cruise ship passengers from the Grand Princess yesterday morning.
"The Red Rebels were there to silently mourn for the loss of extinct animals and the ones that we are currently losing."
Six "Red Rebels" were there and three Extinction Rebellion protesters were supporting them by handing out flyers and answering questions from the public.
The Red Rebels were walking around the Octagon and taking trips down to the train station and back as part of their silent protest.
Mr Cockle said most of the cruise ship passengers received their brochures and the protest well.
"We did make sure that we said to them that what we are handing you is sad news and we want you to feel welcome and have a good time while you’re here, but we also want to tell people what’s going on.
"Some passengers spoke about the concerns they have for their grandchildren and agreed we need to do more as a society to reduce the harm that we are causing to the environment."
Mr Cockle said carbon dioxide emissions per kilometre attributable to a typical cruise ship passenger was about three to four times that of an economy class plane passenger.
On top of the pollution caused by ship’s exhaust fumes, cruise ships have been caught discarding rubbish, fuel and sewage directly into the ocean, he said.
