Oh the places you'll go...

Want to see some wildlife?  Your best bet for alligators at the causeway.  A lot of nice walking paths and a nature center, plus a very nice beach, and the south jetty you can walk out on (if you are up for a LONG walk).

For a morning or afternoon of (relatively) cheap fun, a head boat is a great option.  For more intimate affairs, private charters are available less than 5 minutes away!

Only 45 minutes away, it's a nice historic town you can enjoy for something a little different.