We cruised Ruby in the Eastern Med last summer. I echo most of what Mike says.
Ruby began our cruise with an over night in Venice. If that is the case you need to be back on board at least an hour before sail away. The Venice departure is beautiful and you should have a port lecturer narrate as you pass through the canal. I recommend finding a place on the bow - go outside on the Promenade deck and then head forward, you need to go up one deck to hit the point.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016
Star Clippers: Royal Clipper 2015