Manatee-watching may not be as consistently rewarding as birding. Often the only sign of the massive creatures are the concentric circles of water swelling upward from their underwater path. But if you keep an eye on the canal leading from Black Point Marina to Biscayne Bay, you'll see a snout poking above the water to snuffle in some of that fragrant Mt. Trashmore air before going back under. Occasionally a manatee's entire bulk will be visible, a sight worth whatever wait it takes.