Since I am from Florida, stingrays are nothing new (I catch rather large ones all of the time (which I release) so the tour that appeals to me most is the most is the Atlantis submarine tour. I have heard a number of good things about it.
Western Caribbeam Carnival 2005
Eastern Caribbean Holland America 2006
Alaska Diamond Princess 2007
Western Caribbean NCL Jewel 2008
Southern Caribbean Holland America Westerdam 2008