Sharks' troubles run deep.
The lagoon and other coastal nursery habitats for sharks are reeling from pollution, fishing pressure and other threats. Sharks that survive to adulthoodthen face an ocean of troubles, from fishermen seeking an adrenaline rush to others after fins for $100 bowls of soup.
"We're killing about 6 1/2 to 8 percent of the sharks out there per year," said Boris Worm, professor of marine biology at Dalhousie University in Nova Scotia.
Shark reproduction, even at its best, can't keep pace with shark deaths. Most shark species are losing ground, including many that roam the Space Coast. Some could face extinction within a decade or two.
And while sharks might not exactly tug at our heartstrings like dolphins and other more cuddly creatures, think about those scallops or that lobster you enjoy. Sharks play such an integral role in the food web that if they vanish, the effect could be felt on your dinner plate.
"They're like slow-moving disasters," Worm said of shark declines. "I think overall, the ball is with the public, with the policymakers. I think scientists have done their work."
Fishing pressure from those who slaughter sharks only for their fins is the main threat.
"This is a global problem. We pick on the apex predators," said Grant Gilmore, a fish ecologist who's studied the lagoon for four decades.
Shark finning has grown more lucrative as China's emerging middle class increasingly desires shark fin soup, a delicacy that quenches upwardly mobile Asian appetites for status.
But finning is not just a Pacific Ocean problem.
"There's finning south of us in the Caribbean and in South America," Gilmore said.
He's even seen evidence of finning off Cape Hatteras, NC.
"There were carcasses laying all over the bottom without their fins," he said.
According to the International Union for the Conservation of Nature Shark Specialist Group, 28 percent of shark species are at risk of extinction.
An estimated 100 million sharks are killed annually, Worm and other researchers estimate, 20 million or more per every fatal shark attack.
And that wholesale slaughter could already be sending dire consequences cascading down the food chain, much to the bane of scallop and lobster lovers.
"What we're finding is that for some of these big species, if you don't have them, you're going to be in trouble," said Michael Heithaus, marine biologist at Florida International University.
He likens the ecological effects to how wolf declines enabled deer population booms.
Researchers suspect the collapse of some lobster and scallop fisheries in recent decades might have been due, in part, to shark declines. The theory: With fewer sharks to eat them, octopuses that feast on spiny lobster can flourish. And rays — no longer fodder for sharks — are free to gobble up bay scallops at will.
In western Australia, fewer tiger sharks resulted in more sea turtles, Heithaus said, and other grazing species that denuded marine plants, the foundation of the food web.
"Without those sharks, you can wipe out large swaths of seagrass beds," Heithaus said.
Shark declines can trigger coral loss, as well. Fish spread disease to larger areas of the reef when fewer sharks are around to keep them in check.
So to better protect sharks, scientists want to know more about their life cycles. By identifying crucial nursery grounds, they hope to improve federal management of large coastal sharks.
But recoveries for many shark species could require decades, because many take 20 years or more to reach reproductive age and have small litters, every other year or so.
Scalloped hammerheads are among the most imperiled. Foreign vessels target them for their high-priced fins, which are used in soups that can cost more than $100 a bowl. The species is easy to catch in large numbers because it schools together.
The meat is considered unpalatable. But the fins are so valuable that fishermen dump the rest of the shark at sea to die, making room for more fins.
Scalloped hammerheads and many other sharks also are killed as "by-catch" in fisheries targeting other species.
Last month, the federal government listed four key populations of scalloped hammerhead sharks under the Endangered Species Act. The move didn't include scalloped hammerheads off Florida's east coast and in the Gulf of Mexico, where strict fishing rules already exist.
While finning is rare — and illegal — off Florida, scientists say the bigger problem here is the drastic drop in lagoon seagrass which has stressed one of the most vital shark nursery habitats.
"The seagrass is the basis of the food chain," Gilmore said. "The food resources have really gone down substantially."
Among the lagoon sharks potentially in peril: bull sharks, scalloped hammerheads and sawfish, to name a few.
The Indian River Lagoon is the most vital nursery habitat for bull sharks on the Atlantic coast.
Large pregnant bull sharks, some upward of 8-feet long, enter the lagoon through Sebastian Inlet and other inlets, usually between May and August. They typically don't eat while in the lagoon but just give birth to their pups and exit the estuary, unbeknownst to swimmers and waders.
Despite the bull shark's reputation as among the most dangerous offshore, there's never been a documented shark attack in the 156-mile-long lagoon.
Scalloped hammerheads and lemon sharks are also known to enter the lagoon, but mostly near inlets.
Another lagoon dweller, the sawfish — an intermediate between sharks and rays — is the Rodney Dangerfield of the shark world. These lowly "flat" sharks garner much less press, fear or respect. But they are among the most endangered shark-like species, and the strangest.
This odd-looking creature swims through schools of mullet, swiping its saw side-to-side, stunning fish to make them easy eating.
Sawfish can grow more than 20 feet and were once commonplace in the lagoon. They have all but vanished from overfishing. While classified as rays, they're primarily shark-like in appearance and closely related to sharks.
In the 1800s, net fishermen wanted to rid the lagoon of sawfish because they ruined nets.
"Some fishermen caught well over 100 sawfish in a single season," Gilmore said.
The 1995 ban on nets that entangle fish by the gills helped sawfish and other Florida sharks rebound, fish biologists say.
"Without question, I think they are rebounding in the southern end of the lagoon," Gilmore said. "We're hearing more and more reports of them."
But collectively, sharks have a long road to recovery, and much of their fate lies far off our shores, says Worm, of Dalhousie University.
Market forces are already starting to make shark fin soup unfashionable in China, he said. "You do see the culture shifting at the marketplace. It's a real race against time, though."