>Although our descent to the bottom is quick, the current pushes us to Zion Train's detached stern. Ninety-foot visibility allows us to catch an early glimpse of what awaits us on the wreck. As we approach, an indistinct mass of slow-moving shadows morphs into a collection of huge fish.
>A similar gathering of 40 or 50 of these behemoths is currently under way nearby on the MG-111, a busted-up barge in 65 feet of water one mile inshore of our current location. Further offshore at a site called Hole in the Wall, named for a giant swim-through in the side of a deep ledge, another 30 or 40 goliaths are gathered. Well to the south, off Boynton Beach at a depth of 110 feet, the 258-foot freighter M/V Castor holds a resident population of 12 goliaths and attracts a few dozen more during spawning season. Just north of Lake Worth Inlet is another group of wrecks (Mizpah, PC-1170 and Amaryllis) that attracts similar numbers of the grouper.
>If not for a federal moratorium enacted in 1990 to protect this one species of fish, the opportunity to witness these aggregations would not exist. Florida is now the only place on the planet where large-scale goliath spawns occur. In terms of accessibility, the Palm Beach coast is it: Thanks to the area's underwater topography, five of the six known goliath-grouper spawning aggregations off Florida's east coast are here.
>Palm Beach is known as a drift-diving destination; currents typically bathe area reefs in a life-giving flow while providing divers with free rides. The currents result from the continental shelf narrowing to less than six miles wide here, which allows the Gulf Stream to sweep in closer to the coast than anywhere else in North America. Running north-south at depths between 45 and 140 feet is a massive ridge composed of ancient limestone. The uneven and undercut bottom contours that these formations create provides ideal habitat for a wide variety of life.
>Sea-turtle encounters are reliable highlights of Palm Beach dives. Seeing fewer than two turtles per dive at any time of the year is considered a bad day. The arrival of spring increases the chances of multiple sightings, with the peak between May and July. This is largely due to the Palm Beaches being a major nesting ground for three of the Atlantic Ocean's five species of sea turtle — loggerheads (Caretta caretta), greens (Chelonia mydas) and leatherbacks (Dermochelys coriacea).
>Leatherbacks are the hulks of the sea-turtle clan, dark grey and black in color, 7 feet long and weighing 1,000 pounds or more when fully mature. Although in-water encounters with leatherbacks are few, meetings with loggerheads and greens are commonplace; these turtles take to the reef's ledges to sleep off their exhaustion following nights on the beach laying eggs in the sand. I can't count how many times I've come across large loggerheads bugged-out with fatigue, with their heads the only part of their bodies they managed to get under a ledge. Seeing one of these 350- to 500-pound ladies in such a peculiar pose is like seeing a Hummer's failed attempt at parking in a tool shed.
>Hawkbill turtles (Eretmochelys imbricata), recognizable by their ornate shells and hawkish, hook-shaped snouts, are also routinely encountered here. Unlike the other species, they do not nest in Palm Beach, but they are often spotted cruising the reefs looking for particular sponges to dine on.
>The close proximity of both the Gulf Stream and the deep Atlantic to the continental shelf creates a relatively narrow corridor that is traveled by a variety of large, nomadic creatures including sharks. The most commonly seen are nurse and Atlantic reef sharks, but resident bulls, lemons, blacktips, guitarfish and sawfish might also be encountered. Even scalloped and great hammerheads, tigers and whale sharks aren't strangers here.
>Sharks and Rays
>Opportunities to see sharks increase between November and April as the northern portion of the Palm Beaches turns into the aggregation center for thousands of spinner sharks. Converging en masse along the shoreline, these 4- to 5-foot sharks give beachgoers a spectacle as they launch themselves from the water with spinning aerobatics.
>In addition to the spinners, the number of bull, sandbar and lemon sharks more than triples as these larger species move down from the north to escape the cold and join the resident populations on the outer reefs and wrecks offshore of Jupiter and North Palm Beach.
>The big thrill for divers fortunate enough to catch the show is seeing large numbers of lemon sharks (Negaprion brevirostris) converge into traveling aggregations. A single aggregation can number more than 100, but groups of 25 to 40 are most common. Adding to this strange spectacle are occasions in which a group will park together on the bottom to nap. This behavior from such large sharks (8 to 9 feet long) makes for a baffling spectacle. Unfortunately, these groups are highly sensitive to noise; divers' bubbles tend to spook them away.
>If sharks, turtles and goliaths aren't enough, divers will also find a variety of rays — from small clearnose skates to large southern and roughtail stingrays and eagle rays. If you're lucky you might even spot a manta in the 20-foot shallows along the beach.
>It is remarkable to think this kind of wildlife exists so close to such a large metropolitan area. But until you see it for yourself, you've got my word on it: It's a happening place.
>Getting There: Dive charters operate out of all four inlets — Jupiter, Lake Worth (Palm Beach), Boynton Beach and Boca Raton, which are all accessible from I-95 or US 1. There are numerous daily flights into Palm Beach International Airport (PBI). For more information on travel, accommodations and topside attractions visit www.palmbeachfl.com.
>For more than 10 years the Blue Heron Bridge at Phil Foster Park, north of West Palm Beach, has been a cherished shore dive for many divers and photographers. Access is easy, and depths are shallow (15 to 18 feet). Incoming tide is best for visibility; it pulls in clearer water through the Lake Worth Inlet. Outgoing tide reverses the flow, reducing visibility from the 40- to 60-foot range down to a muddy 5 or 10 feet.
>Blue Heron Bridge
>"The bridge" is regarded a muck dive; the bottom around its pilings is largely made up of sand, rubble and discarded debris. The attraction is the wondrous variety of small fish and invertebrates that are rarely seen in Florida or even the Caribbean. But one must study the surroundings, scanning every nook, cranny and empty bottle to find the little treasures that exist here. These include seahorses in shades of brown, bright red, yellow and orange; blue and yellow nudibranchs; funky-looking batfish; sea robins; stargazers and a few varieties of frogfish (the striated frogfish being the most common but best camouflaged).
>Not all the marine life here is at the small end of the spectrum, though. The larger inhabitants include barracuda, snook, spotted eagle rays and even manatees.
>Getting There: Take I-95 and exit at Blue Heron Boulevard, just north of West Palm Beach. Head east to Singer Island, driving through Riviera Beach and over the first span of the Blue Heron Boulevard Bridge. As you pass over the larger span of the Blue Heron Bridge, the entrance to Phil Foster Park is on the left.
>Palm Beach, Fla., Gallery