If you’re driving down the Overseas Highway, past the endless stretches of turquoise water and those kitschy shell shops, you’ll eventually hit Marathon. Most people just blast through on their way to Key West. They’re in a rush to hit Duval Street. They want the sunset celebration at Mallory Square. But honestly? They’re missing out on some of the best seafood in the entire Florida Keys. Big Mac and Little Lu's isn’t just a restaurant with a slightly quirky name; it’s a local institution that manages to stay grounded even as the Keys get more and more "resort-ified" every year.
It’s a fish market. It’s a restaurant. It’s basically a temple to fresh catch.
You walk in and the first thing you notice isn't the decor—it's the smell of the ocean, but in the good way. The way that tells you the hogfish on the ice at the front was probably swimming six hours ago. Capt. "Big Mac" and his wife "Little Lu" (and their kids who help run the place) have built something that feels like a backyard party where everyone happens to be a professional chef.
The Reality of Freshness at Big Mac and Little Lu's
The "Big Mac" in the name is Captain Mark, a guy who actually knows what the bottom of the Atlantic looks like. He's been a commercial fisherman for decades. This matters because, in the world of Florida seafood, "fresh" is a word that gets thrown around way too loosely. You’ll see "Fresh Seafood" signs at gas stations. You’ll see it at tourist traps that are actually defrosting vacuum-sealed tilapia from halfway across the world.
At Big Mac and Little Lu's, the supply chain is basically a straight line from the boat to the back door.
I’ve seen plenty of places try to fake the "salty local" vibe with corrugated metal and some old nets. Here, it’s authentic because it’s functional. When you eat here, you’re sitting amongst the locals—the construction workers, the boat captains, and the families who live in Marathon year-round. It’s loud. It’s busy. It’s great.
Stone Crabs and the Art of the Seasonal Wait
If you happen to be there between October 15th and May 1st, you’re in stone crab territory. This is serious business in the Keys. Most people don't realize that stone crabs are a sustainable fishery because the hunters only take one claw and drop the crab back to grow it back.
At Big Mac and Little Lu's, they don’t mess with the classics. They serve them cold. They serve them cracked. You get that mustard sauce that’s slightly sweet and very tangy.
- Large claws
- Jumbo claws
- Colossal (if the ocean was feeling generous that day)
Prices fluctuate. They’re based on the daily market rate. Don't act surprised if the price on the board is different than what you saw on a Yelp review from three years ago. That’s just how the ocean works. If the weather is rough and the boats can’t get out to pull the traps, there are no crabs. Simple as that.
What You Should Actually Order (And What to Skip)
Look, everyone goes for the Fried Shrimp. And yeah, they’re good. They’re huge, they’re crunchy, and they aren't greasy. But if you really want the Big Mac and Little Lu's experience, you need to look at the board for the daily specials.
Hogfish. If it’s on the menu, get it. Hogfish is the local darling because it’s a diver-caught fish. You can’t really catch them on a hook and line very easily because they eat crustaceans. They have this delicate, scallop-like flavor that gets absolutely ruined if you overcook it. The kitchen here knows how to treat it. They usually offer it "Francaise" style or blackened. Both are solid choices, but honestly, just get it sautéed with a little lemon and butter.
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And then there's the Conch Chowder.
There are two types of people in the Keys: Red and White. Red is the Manhattan-style, tomato-based Bahamian chowder. White is the creamy, New England-style. Big Mac and Little Lu's usually leans into that spicy, hearty red conch chowder that clears your sinuses and warms your soul. It’s packed with conch, which—if you’ve ever tried to cook it—is tough to get right. It can be like chewing on a rubber band if the chef is lazy. Here, it’s tender.
Why the Fish Market Side Matters
Half the building is a seafood market. This is the secret weapon. If you’re staying in a rental house in Marathon or Big Pine Key, do yourself a favor and buy a couple of pounds of Pink Gold shrimp or some snapper fillets to take home.
They also sell their house-made sauces and spices. The "Big Mac" seasoning is one of those things you’ll buy a bottle of, use it twice, and then wish you’d bought five more when you get back home to Ohio or wherever.
The Atmosphere: Don't Expect White Tablecloths
If you’re looking for a romantic, candlelit dinner with a sommelier, keep driving until you hit some fancy resort in Islamorada. Big Mac and Little Lu's is a "flip-flops and a t-shirt" kind of place.
The service is fast, but it’s Keys-fast, which means "island time" is still a factor. The servers are usually juggling ten things at once, yet they still manage to remember that you wanted extra lime for your tacos. It’s endearing. It feels like a family-run business because it is one.
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One thing people get wrong? They think because it looks like a "shack," it’s going to be dirt cheap.
Quality seafood isn't cheap.
Ever.
Fuel for the boats is expensive. Insurance is expensive. The labor of hauling traps and cleaning fish is grueling. You’re paying for the fact that the fish was likely in the water while you were sleeping this morning. It’s worth the premium.
The Key Lime Pie Litmus Test
You can't talk about a Keys restaurant without mentioning the pie. Every place claims to have the "best" or the "original" or the "award-winning" version.
The version at Big Mac and Little Lu's is solid. It’s tart. It’s got a graham cracker crust that actually tastes like butter, not cardboard. It’s not that neon-green monstrosity you see in tourist traps. It’s the real deal—pale yellow, just like the juice of an actual Key Lime.
Practical Tips for Your Visit
- Check the Hours: They aren't open 24/7. In fact, they sometimes close earlier than you'd expect, especially during the off-season. Always check their social media or call ahead if you're making a special trip.
- The Parking Situation: The lot is a bit tight. If it’s prime dinner time, you might have to circle once or twice. Be patient.
- Lunch vs. Dinner: Lunch is usually a bit more laid back and features great sandwiches (the blackened mahi sandwich is a personal favorite). Dinner gets the heavier hitters like the full seafood platters and the more elaborate fish preparations.
- The "Little Lu" Factor: Often, you'll see Lu herself behind the counter or managing the floor. If you have questions about where the fish came from or how to cook something you bought from the market, just ask. They love talking about their craft.
It’s easy to get cynical about the Keys. Between the traffic on US-1 and the rising prices, sometimes it feels like the "old Florida" is disappearing. But places like Big Mac and Little Lu's are the holdouts. They remind you why people started coming down here in the first place—for the sun, the water, and the incredibly good food that comes out of it.
How to Make the Most of Your Stop in Marathon
If you’re planning a trip, don't just eat and leave. Marathon has a lot more going on than it gets credit for.
- Visit the Turtle Hospital: It’s just down the road. They do incredible work rescuing and rehabilitating sea turtles. It's a great way to kill an hour while you're waiting for your appetite to come back after a big lunch.
- Walk the Old Seven Mile Bridge: Head down to the 64-mile marker and take the walk out to Pigeon Key. The breeze is incredible, and you can see the rays and sharks swimming in the water below.
- Buy the Smoked Fish Dip: Before you leave the fish market at Big Mac's, grab a tub of the smoked fish dip and some crackers. It’s the perfect snack for when you finally reach your hotel and realize you’re too tired to go out again.
The Florida Keys aren't just a destination; they’re a lifestyle that revolves around the tides. Big Mac and Little Lu's understands that better than most. They aren't trying to be the trendiest spot on Instagram. They’re just trying to serve the best fish in the Middle Keys. And honestly? They’re succeeding.
Next Steps for Your Keys Adventure:
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To truly experience the best of Marathon, aim to arrive at Big Mac and Little Lu's during the mid-afternoon "sweet spot" between 2:00 PM and 4:00 PM. This avoids the heavy lunch and dinner rushes, giving you better access to the fish market staff who can explain the day's specific landings. After your meal, head five minutes south to Sombrero Beach—one of the few high-quality sandy beaches in the Keys—to catch the late afternoon light. If you are buying fresh fish to travel, bring a high-quality cooler; the market provides ice, but the Florida heat is unforgiving on a drive back to the mainland. For those staying locally, ask the market staff for their "pan-sear" tip of the day, as they often have specific advice for whatever species (like mutton snapper or yellowtail) is running particularly well that week.