10 shells, 13 marine species, 6 known hazards, and 5 conservation projects.
“The sea, once it casts its spell, holds one in its net of wonder forever.” — Jacques Cousteau
Gentle, slow-moving marine mammals that graze on seagrass. Can weigh up to 1,200 pounds. Often spotted in the warm shallows of Biscayne Bay.
Completely harmless. Keep 50 feet of distance — it's a federal crime to touch, chase, or harass manatees (Marine Mammal Protection Act).
Manatees are more closely related to elephants than to any other marine mammal. They constantly grow new teeth from the back of their jaw that push forward — like a conveyor belt — replacing worn-down front teeth.
The most common nesting sea turtle on Miami Beach. Females haul out onto the sand at night from May through October to lay eggs in deep nests.
Do not approach nesting females, touch eggs, or use flashlights on the beach at night during nesting season. Light disorients hatchlings. Keep 30+ feet away.
Loggerheads navigate thousands of miles using Earth's magnetic field. A female born on Miami Beach will return to the exact same stretch of sand 20-30 years later to lay her own eggs.
Named for the green color of their fat (from a seagrass diet), not their shell. Juveniles are common in the seagrass beds of Biscayne Bay.
Federally endangered. Same rules as loggerheads — do not approach, touch, or illuminate with lights during nesting season.
Green turtles are the only herbivorous sea turtle species. They act as living lawn mowers for seagrass beds, and their grazing actually keeps the grass healthier — like mowing your lawn helps it grow thicker.
The largest living turtle — up to 7 feet long and 2,000 pounds. Their shell is soft and leathery, not hard like other sea turtles. Extremely rare on Miami Beach.
Critically endangered. If you see one nesting, do not approach. Call FWC Wildlife Alert: 888-404-FWCC.
Leatherbacks can regulate their body temperature, making them the most cold-tolerant reptile on Earth. They've been tracked diving to 4,200 feet — deeper than most submarines operate — to hunt jellyfish in pitch darkness.
Slow, bottom-dwelling sharks commonly seen resting under ledges and dock pilings. The most commonly encountered shark in South Florida waters.
Generally docile but will bite if stepped on, grabbed, or cornered. Their bite is extremely strong — they latch on and don't let go. Never touch a resting nurse shark.
Nurse sharks can breathe while lying still on the bottom by pumping water over their gills — most sharks must swim constantly to breathe. Their name likely comes from the sucking sound they make when feeding, resembling a nursing baby.
A flat, diamond-shaped ray that buries itself in the sand with only its eyes showing. The most common cause of beach-related injuries in South Florida.
Do the 'stingray shuffle' — slide your feet along the bottom instead of stepping. This bumps them and they swim away. A stepped-on ray reflexively stings with a barbed, venomous tail spine. Hot water immersion (110°F) is the treatment.
Stingrays have electroreceptors that can detect the faint electrical fields produced by the muscles of buried prey. They essentially have a sixth sense — they can find a clam buried 6 inches under the sand without seeing or smelling it.
A spectacular ray with a duck-bill snout and a dark back covered in white spots. Often seen 'flying' through the water in graceful groups.
Rarely a threat. They have venomous tail spines but are shy and flee from humans. Observe from a distance. Occasionally leap fully out of the water — give boats space.
Spotted eagle rays have flat, plate-like teeth designed to crush shells. They dig up clams and oysters from the sand and crunch through them like potato chips. They sometimes leap 6+ feet out of the water — possibly to dislodge parasites.
A sleek, torpedo-shaped predator with a mouth full of razor-sharp teeth. Curious and bold, they often follow snorkelers but almost never attack.
Avoid wearing shiny jewelry while swimming — it mimics fish scales and may attract a strike. Bites are extremely rare but can be serious. They're curious, not aggressive — don't panic if one approaches.
Barracudas can accelerate from a standstill to 36 mph in a single burst — faster than a great white shark. Their bite force is among the strongest of any fish relative to size. In some Caribbean regions, eating large barracuda causes ciguatera poisoning.
Brilliantly colored reef fish with a beak-like mouth that crunches coral. The sand on Miami Beach? A significant percentage of it passed through a parrotfish.
Completely harmless to humans. A critical reef species — never harass or spear parrotfish (harvest banned in many areas).
A single large parrotfish produces up to 840 pounds of sand per year by eating coral, digesting the algae, and excreting the calcium carbonate skeleton as fine white sand. They also secrete a mucus sleeping bag at night that masks their scent from predators.
A small, bold damselfish with five distinctive black bars on a yellow-silver body. Named for its stripes resembling a military sergeant's chevrons.
Harmless, though nesting males can be surprisingly aggressive — they may nip at snorkelers who get too close to their purple egg patches on rocks.
Male sergeant majors turn from yellow-silver to dark blue-black when guarding eggs. They fan the eggs constantly with their fins to keep them oxygenated and fiercely attack anything that comes near — including fish 10 times their size.
The clawless lobster of South Florida. Unlike Maine lobsters, spiny lobsters have long, spiny antennae and no large crushing claws.
Sharp spines on the shell and antennae can scratch. Mini-season (last Wednesday of July) brings heavy diver traffic — stay alert in the water.
Spiny lobsters navigate by detecting Earth's magnetic field, similar to sea turtles. During autumn cold fronts, they form single-file marching lines of up to 60 lobsters, each touching the tail of the one ahead — a 'lobster conga line' that can stretch for miles.
A living fossil unchanged for 450 million years — older than dinosaurs by 200 million years. Despite the name, more closely related to spiders than crabs.
Completely harmless despite their appearance. The tail spike is not a stinger — it's just a rudder for steering. Do not pick them up by the tail (it can damage them). Support from underneath.
Horseshoe crab blood is copper-based (turns blue when exposed to air) and contains a chemical called LAL that detects bacterial toxins. Every injectable medicine and vaccine is tested with horseshoe crab blood. A quart of their blood is worth $15,000.
Translucent, saucer-shaped jellyfish with four horseshoe-shaped reproductive organs visible through the bell. The most commonly encountered jellyfish on Miami Beach.
Mild sting — most people barely feel it. Some experience slight tingling or minor rash. Dead ones on the beach can still sting. Rinse with saltwater (never fresh water). Vinegar for persistent sting.
Moon jellyfish are 95% water. Despite having no brain, heart, or blood, they've survived for over 500 million years. Some species can reverse aging — transforming back from adult to polyp stage — making them theoretically immortal.
Know these threats. Most encounters are avoidable with awareness.
NOT a jellyfish — it's a siphonophore: a colony of specialized organisms working together as one. The blue gas-filled float (pneumatophore) sits above water like a sail while tentacles trail up to 165 feet below.
Iridescent blue-purple gas bladder (2–6 inches) floating on the surface like a small balloon. Trailing blue tentacles that are often nearly invisible in water. Dead ones on the beach are still bright blue-purple.
Several species of box-shaped jellyfish occur in South Florida waters. Unlike the famously lethal Australian species, the local species cause painful but rarely life-threatening stings.
Cube-shaped (box) bell rather than the dome shape of typical jellyfish. Transparent to pale blue. Tentacles trail from the four bottom corners. Small — usually 1-3 inches across.
A beautiful but devastating invasive species from the Indo-Pacific. Their venomous spines and voracious appetite threaten Florida's native reef ecosystems. Removing them is encouraged.
Unmistakable: red/white/brown zebra stripes with elaborate feathery pectoral fins and 18 venomous dorsal, pelvic, and anal spines. 6–15 inches. Found on reefs, wrecks, jetties, and even dock pilings.
Not actually a coral but a hydrozoan — a relative of jellyfish. Looks like mustard-yellow branching or plate-like coral. Causes a burning sting on contact that develops into an itchy rash.
Mustard yellow to brownish-yellow branching or blade-like formations. Smooth surface without the visible polyps of true coral. Often encrusts rocks, wrecks, and even other corals. White tips on branches.
Black urchins with extremely long, thin, brittle spines that break off in skin on contact. Found on rocky areas and jetties. The spines are mildly venomous and can cause intense pain.
Round, black body with very long (6-12 inch) thin black spines radiating in all directions. Found on rocks, jetty walls, and reef crevices in shallow water. Spines track movement — they point toward approaching shadows.
Masters of camouflage that look exactly like algae-covered rocks. While the famously lethal stonefish doesn't occur in Florida, the related spotted scorpionfish delivers an extremely painful venomous sting from dorsal spines.
Nearly impossible to see — they look like a rock or clump of algae. Mottled brown/red/gray, lumpy body, 8-14 inches. Usually motionless on the bottom near rocks and reefs. Feathery pectoral fins and a large upturned mouth.
A visionary 7-mile underwater public sculpture park and artificial reef running parallel to Miami Beach. Designed by world-class architects and artists, it combines art, marine science, and coastal resilience into a snorkel-accessible underwater trail.
A hands-on citizen science program run by UM's Rosenstiel School of Marine, Atmospheric, and Earth Science. Volunteers dive to outplant lab-grown coral fragments onto degraded reefs, directly rebuilding Florida's coral reef tract.
FWC coordinates the monitoring and protection of over 100,000 sea turtle nests annually on Florida beaches. Miami-Dade has one of the highest nest densities in the state. Local volunteers patrol beaches daily from May through October.
A coalition of Miami-Dade County, UM, and citizen scientists monitoring the health of Biscayne Bay — the primary marine habitat supporting all the species in this guide. The bay suffered a mass fish kill in 2020 from nutrient pollution and oxygen depletion.
Multiple organizations are actively replanting coral along the nearshore reef tract. The Florida Coral Reef Tract — the only barrier reef in the continental US — has lost over 90% of its coral cover since the 1970s. Restoration efforts focus on heat-resistant genetic strains.