Atlantis is doing a gay cruise from Port Liberty in New York on the Anthem of the Seas. This is the newest and most advanced Royal Caribbean ship and has space for 4200 guys.
New York (Cape Liberty)
Port Canaveral, Florida
Coco Cay, private cruise line island, Bahamas
Atlantis cruises attract mostly gays, and usually a few lesbians. Average age range is about 27-50, some younger and some older guys. The concept is all about making everybody happy, day time entertainment at the pools, have nice dinners with (new) friends, see fun shows in the theatres, and 1 or more parties till the sun comes up.
Some of the parties have themes (whiteparty, classic disco, tropical etc), and most of the guys really dress up for those. Watch the Youtube video to get an impression. Many also decorate their cabin doors.