Substances can happen.
They can be found anywhere, not just where they are legal.
I have smelled wacky tabbaki on a couple of cruise but since it did not envolve me, there was no problem.
Carnival Liberty New Year's Eve 2007
Liberty of the Seas 5/2008+11/2009
Allure 1/16/ 2011
Booked Vision of the Seas . 2/14/2015
Booked Allure of the Seas... 2/21/16 *Last Gang Cruise*