capybara
Contributor
Bird's runs a great manatee snorkel trip. You might want to try Devil's Den too; it's a shallow cavern (with air overhead so you can do it with just open water certification). The only life there are catfish that you can feed, but it's still cool swimming around the rock formations. We did both of those and had a great time. Blue Grotto is nearby so you could do both Devil's Den and Blue Grotto in one day. We had planned on diving West Palm Beach but missed out because of colds. It's supposed to be good diving though. It is a fairly long drive already to get to WPB from Crystal River (Florida is surprisingly big!) so you may not want to go all the way to the Keys.