If you want to assemble a group of 8 passengers so you can benefit of sharing costs I would recommend you to sign up on a website called Cruise critic. Once signed in, go to Roll Call, here members travelling on the same cruise liner arrange to group up with other passengers to do shore excursion together to reduce prices, I am aware of this because many of my customers have grouped up for my excursion through Cruise Critic: http://www.cruisecritic.com.

Members on Cruise Critic travelling on the same cruise liner arrange to group up with other passengers to do shore excursion together to reduce prices, I am aware of this because many of my customers have grouped up for my excursion through Cruise Critic.