Check Carnival's website for its smoking policy, but I believe you are correct regarding e cigarettes.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
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
On my last couple of cruises, I've noticed that they made a point of letting everyone know that "vaping" was not allowed, anywhere that "smoking" was not allowed. Prior to that, I'd noticed people "vaping" in the theater, in the dining room, and just about everywhere else on the ships. Perhaps these people caused the change in policy?