If you're planning a trip to Florida and want to see manatees in their natural habitat, November through March is usually your best bet. During these months, the water temperatures drop low enough that manatees congregate around warm springs and power plant discharge canals. I've had some great experiences spotting them at Blue Spring State Park near Orange City during this time of year, but keep in mind that it's also peak tourist season so get there early if you want a good spot to watch.
