Tarpon, Sea Turtles (many) one Manatee, beautiful palms full of coconuts, huge fish and lots of boaters were experienced at sunsets each night.  There you can walk on the old bridge, fish, or just hang out and watch the beautiful skies.  Lots of friendly folks.     Get there at 7, sunset at 8, gorgeous skies till 9.

Another great spot for sunset shots is the Keys Fisheries restaurant in Marathon. They have a sunset deck up high to watch from.