Located just 6 miles off Key Largo is a U.S. Navy Landing Ship Dock, the latest artificial wreck site to hit the Keys -- or, rather, to be submerged 130 feet below the Keys.
The Florida Keys Dive Center, U.S. 1 at MM 90.5, Tavernier (tel. 305/852-4599; www.floridakeysdivectr.com), takes snorkelers and divers to the reefs of John Pennekamp Coral Reef State Park and environs every day. PADI (Professional Association of Diving Instructors) training courses are available for the uninitiated. While some people have complained that employees are rude here, others disagree; I suggest you decide for yourself. Tours leave at 8am and 12:30pm; the cost is $30 per person to snorkel (plus $9 rental fee for mask, snorkel, and fins), and $65 per person to dive (plus an extra $20 if you need to rent all the gear).
At Hall's Dive Center & Career Institute, U.S. 1 at MM 48.5, Marathon (tel. 305/743-5929; www.hallsdiving.com), snorkelers and divers can dive at Looe Key, Sombrero Reef, Delta Shoal, Content Key, or Coffins Patch. Tours are scheduled daily at 9am and 1pm. You'll spend 1 hour at each of two sites per tour. If you mention this book, you'll get a special discounted rate ($5-$10 off) of $35 per person to snorkel (additional gear $11) and $45 per person to dive (tanks $8.50 each).