Five times since 1992 we've tooted the horn for Biscayne National Park, always for the right reasons. Mind if we do it again? (1) Unlike John Pennekamp Coral Reef and State Park in Key Largo, this national park severely restricts the number of commercial operations carrying people to the reef. In fact only a single concessionaire (Divers Unlimited) is allowed to launch one boat per day with a maximum of 45 people. Compare that to the estimated one million divers annually who swoop down on Pennekamp. (It's the same reef system, by the way.) So you'll never have to fight sunburned tourists for reef space at Biscayne. (2) Because Pennekamp is essentially unrestricted, it has suffered badly at the hands (and flippered feet) of well-meaning but ignorant novices. Not so Biscayne. Dive operators there are fond of saying their reef looks like Pennekamp 20 or 30 years ago. And a healthy reef means lots of sea life: clown fish, triggerfish, parrotfish, barracuda, eel, the occasional shark, and much more. (3) The total Biscayne experience is simply more pleasant than Pennekamp. Departing daily at 1:30 p.m. sharp, the boat cruises across the bay toward its passage between Elliot and Boca Chita keys, then out to the reef and the open Atlantic. It's a relaxing and beautiful journey, both ways. You arrive back at park headquarters between 4:30 and 5:00. (4) At $27.95 the price is right and includes rental of all equipment: mask, snorkel, fins, and safety vest (wet suit extra). You can also bring your own, of course. (5) Biscayne National Park is much closer to Miami than Pennekamp, which makes for a leisurely day trip, and you don't have to hassle with traffic heading to the Keys. Note that reservations are strongly recommended.