Doug saw more animals than I did, but we did both see a manatee.  We were sitting at a covered bar/restaurant at the City Marina (I think the name was Captain Run Aground) getting out of the hot sun and eating lunch when a manatee started to swim slowly by.  It was huge, maybe 18 to 20 feet long, gray with a lot of growth on its back and propeller scars too.  It swam very slowly, when one guy from the bar said it was after fresh water. He got a hose out and turned the water on, splashing it on the surface.  Hearing the sound of the water splashing, the manatee turned around and raced to the sound  (OK,   "raced" for a manatee, maybe 3 mph).  When it got there it took the hose in its front fins, stuffed it in its whiskered mouth and slowly sank to the bottom, drinking the fresh water.  The guy said it would sometimes drink as much as 100 gallons, then would rest on the bottom for awhile and then come to the surface to drink a few gallons more.  I'm not sure I believe him about the 100 gallons, but it was definitely looking for it that day.

Snorkeling off Loggerhead key, a 15-20 inch barracuda swam within a few feet of me in incredibly clear water.  There were also some sort of "jack" fish swimming by and later I was surrounded by thousands of bright blue - almost neon blue - fish, each about a half inch long.  There were green turtle off the Marquesas islands, lots of frigate birds everywhere, and gulls galore.  Migrating birds included a few purple martins, and a lot of small, fast, miserable, non-descript brown sparrows.   

There was also the only significant nesting colony of sooty terns in the US on Bush Key in the Dry Tortugas.  The birds NEVER stopped squalking, day or night, and really went crazy if a frigate bird flew over the colony.  I anchored fairly close to the colony but slept well despite the noise.