Biscayne National Park - http://www.nps.gov/bisc

One of the few marine parks that the NPS manages,
less than a crow's flight from the bustle of Miami.
The half day snorkel boat excursion is well worth
the money (@ $35pp) to see coral and sealife up close.

For more photos, visit http://www.pbase.com/ambadale/florida_2005