Beach Snorkeling: MacArthur Beach State Park

Florida’s Reef Tract is one of largest and most diverse in the world (third in size behind Australia’s Great Barrier Reef and Belize’s Barrier Reef). The close proximity to the Gulf Stream brings a diverse and sometimes bizarre range of marine life to these underwater ecosystems, making Florida’s barrier reef system one of the most prolific and inspiring in the world. One of the truly unique attributes of the reef tract comes from a specific type of reef feature, Anastasia limestone rock that ranges from St. Augustine to Boca Raton. Made of coquina, a mix of mollusc, trilobite, brachiopod and other invertebrate shells, Anastasia rock formations have come to define some Florida beaches (e.g. Blowing Rocks and Coral Cove on Jupiter Island). These rocky outcroppings along the shore extend well out under the surface of the Atlantic, creating some magnificent reefs that are easily accessible by foot and a short swim. 

Rock Reef at MacArthur Beach State Park

The rock reef at MacArthur Beach State Park

   John D. MacArthur Beach State Park is one such beach. The rock reef at MacArthur is easily seen from shore, sometimes peaking out of the surf on lunar low tides, and is quite an interesting snorkel opportunity for the boater averse. As a state park there is a fee for visitors ($5 per vehicle—up to eight people), but that fee is a mere pittance for what visitors get in return. The park itself, nearly 500 acres, covers four unique terrains that gives a glimpse of what primordial Florida must have looked like before Colonial explorers conquered the Seven Seas. Four diverse habitats: maritime hammock; a vast tidal estuary; towering sea dunes; and the underwater world of the rock reef, make MacArthur beach a must visit for locals and tourists. But for this piece, we’re concentrating on the rock reef as one of Palm Beach County’s best easy access snorkel spots.

   Heading to MacArthur Beach, skin divers need to heed a few bits of information: As I mentioned before, there is admission to park; the distance from the parking lot to the beach can seem daunting to some, but there is a tram service; the place can get quite crowded on the weekends, especially during summer; the reef is shallow, especially at low tide, so if you’re into diving deep, check your tides; and boaters frequent the reef, coming in right on top of snorkelers, anchoring directly on the reef, so proceed with caution—dive flags are a must, though there is usually one already out there.  

A Hairy Blenny on the Reef at MacArthur

A hairy blenny on the reef.

 The reef is largely Anastasia rock covered with a unique dweller that has helped grow the reef into a branching and mounding structure. The Saberllariid worm (also known as the reef-building tube worm) is an industrious maritime builder, creating tube-like domains from ocean sand, which, when connected to neighboring worm brethren, form mounding colonies and an extensive reef structure. It has been posited that this tireless worm species may have been instrumental to the construction and preservation of Florida’s beaches through geologic time by creating these vast colonies on beachrock in and near the surf zone [Species Profiles: Life Theories and Environmental Requirements of Coastal Fishes and Invertebrates (South Florida):Reef-Building Tube Worm; Zale and Merrifield]. There are even some that believe these worms, an ancient sea creature, may be partially responsible for the barrier islands of Palm Beach and the less so Singer Island.

   Found from Florida down to the Rio Grande do Sul near Santa Catarina in Brazil, the Saberllariid worm form colonies in the intertidal (the break zone) and subtidal (just seaward of break zone), feeding on micro-plankton in the churned up, sediment-laden waters where corals cannot establish a foothold due to the turbidity. Like coral reefs, Saberllariid reefs are important, both ecologically and geologically, creating habitat for a diverse menagerie of marine life, while also providing a break zone, protecting against beach erosion and storm surge. The close proximity to the beach actually helps with beach renourishment and reclamation, while partially preventing beach erosion from the constant and undaunted Gulf Stream and its steady northern flow, and sands natural tendency to travel south toward the equator (think of Earth as a giant centrifuge).

Sergeant Majors at MacArthur Beach State Park

   The rock reef created at MacArthur is an interesting change of pace from the deeper coral reefs, artificial reefs that dot the South Florida coast, and the man-made structure along the Intracoastal Waterway. Distinctively muted in comparison to the bright subtropic coral reefs, the rock reef is mainly that, brown Anastasia rock with bulbous mounds and branching structure from the Sabellariids, though there is a splotched vibrancy, especially with the bold blotches of fire-red algae throughout and some neon green plants. The depth varies depending on tide, with the reef breaching the surface on heavy low tides and about four to six feet deep, while at high tide the depth can reach close to ten feet. The reef itself is accessible from the beach with just a short swim, no more than 30 to 50 yards.

   There is plenty to see at MacArthur’s rock reef, with marine life of various degrees flocking to the outcropping dependent on time of year, tide cycle, and time of day. On a recent summer visit, small snook were schooling on the deeper section of the reef; the usual reef suspects like sergeant majors, yellow chub, a multitude of snappers (gray, dog and schoolmasters) and grunts (white, French, porkfish, sailors choice, and bluestriped) schooled throughout the reef, especially under ledges; ballyhoo and a school of either adolescent blue runners or yellow jack came though on a northern jaunt; while crabs (a handful of stone crabs in the darker crevices), some small shrimp, and quite a few urchins were roaming the surface. Though there were none in sight while I was there, the reef is frequent stop of loggerhead and green turtles, as well as Caribbean squid, and the occasional shark and ray.

   Though I did not see any while snorkeling, stingray season runs from spring to fall (April to October), with rays of all ilk cruising the beaches and estuaries looking for food and spawning opportunities, so it behooves divers and waders to bust out the old ‘Stingray Shuffle’ when wading out in the shallows. The close proximity to the inlet and the relatively dense reef population at the rock reef makes MacArthur beach a hotbed for stingrays, so look out, and shuffle those feet—a barb to the foot can ruin beach day in a hurry, especially at MacArthur (there is no life guard and that walk back to the visitor center will feel like miles).

Yellow Chub and Pork Fish

Type of snorkel spot: Anastasia rock reef and Saberllariid worm (reef-building worm)

Depth: Roughly 5 to 12 feet

Accessibility: Car/foot

What to Bring: Mask, snorkel and fins; dive flag; refreshments (though there is a Welcome Center/Gift Shop with stuff for purchase)

When to go: Calm flat surf. The reef is in the break zone, so during heavy surf the reef can be dangerous.

Avoid: Boaters, they pull-up right along the reef and anchor with little regard for snorkelers—be vigilant.

What to see: Tropical and reef fish; invertebrates and crustaceans; sea turtles; the occasional shark (especially in October and April)

What to leave at home: Spears and Hawaiian slings. Though you may fish here, you cannot spear from the beach.

Park Extras: For those that are truly new to snorkeling, or do not feel comfortable tackling the reef by oneself, join park rangers for an Intro to Snorkeling class. Guests will learn the basics on equipment, how to use it, diver safety, and techniques. If weather permits, rangers may take the class to the beach for a quick equipment test. Free with park admission; reservations are required: call 561-624-6952.

MacArthur Beach State Park

Tips: Before you head to MacArthur Beach State Park, check on the surf and visibility. If the visibility is shot, there won’t be much to see, and if the surf is heavy, forget snorkeling and grab a board. Avoid touching the reef. Though not so much as a coral reef, the Saberllariid worm structure is still delicate, especially when an errant snorkeler gets pushed into the reef from a wave. When you arrive at MacArthur, check out the Nature Center before hiking on down to the beach. The Nature Center gives visitors a detailed description of the four distinct habitats at MacArthur, as well as three educational videos in the theater. I would suggest walking the boardwalk on the way to the beach. It gives you a chance to check out the estuary between the maritime hammock and the dune—there is plenty to see, from wading birds to fish, rays, even dolphin, and manatee at high tide. But on the way back to the car, opt for a tram ride—it is much quicker.

MacArthur Beach State Park Rock Reef

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