There are several gay / gay friendly boat operators that will take you out for the sunset. This site does not allow me to post commercial links so just do a search for SEBAGO CATAMARAN and BLU Q Catamaran.
Sebago is a all gay Saturday nights and mixed most other nights. BLU Q is all gay. Be sure to call ahead and tell them you are with a cruise so that they get you back to the ship on time. If they cannot, go down to the northern end, and hang out around Mallory Square. You would hang a left when you exit the ship.
There are several other smaller boat operators that have flyers in the bars. The gay bars on Duval Street are walking distance from the cruise ships. Walk straight (galy forward) from the ship to Duval and turn right for the gay bars.
*****If you want to avoid the touristy crowd altogether, go to Duval hang a right and walk all the way to the end and look for Atlantic Shores. It is a bit of a walk but well worth it. It is my favorite. You will not get much of a sunset view but the is a great T-Dance on Sundays. Do search for Atlantic Shores Resort. It is adverstised as clothing optional but 99% are clothed. It is a fun atmosphere…not overly cruisy.
Enjoy. I wish I was there.