It started that January with a small patch of discolored water about 20 miles west of St. Petersburg. Six months later, its lethal touch left scores of dead sea life on the shores of Pinellas County.
Soon, it was deemed one of the worst outbreaks of Red Tide in state history.
That was the algal bloom of 2005, which spent more than a year plaguing the gulf from the Alabama border to the Florida Keys.
Now, 13 years later, another devastating eruption is tainting the beaches of Southwest Florida and slowly tiptoeing north toward Tampa Bay.
Back then, in the coastal towns and cities largely dependent on visitors, tourism fell and businesses suffered.
Back then, locals grumbled as they took cover behind masks. The same toxins so deadly to sea life also caused respiratory problems for humans.
Back then, the impact was so catastrophic that it created a "dead zone" in the Gulf of Mexico.
Is it about to happen again?
"This Red Tide is stronger than anything I've ever seen before," said Sarasota charter boat captain Wayne Genthner, who remembers 2005 well. "It seems to be killing quicker."
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Scientists say the naturally-occurring phenomenon has been plaguing the state since the 1800s, but putting each instance of Red Tide in a historical context is difficult because record-keeping didn't start until the 1950s.
The 2005 outbreak was believed to be the worst to hit Florida since the 1971 one. And what happened 13 years ago is indicative of what the bay area may soon have to deal with again.
Red Tide made National Geographic magazine and the front page of newspapers across the country in 2005. Perplexed scientists from all around speculated why Karenia Brevis, the alga that causes the bloom, struck with such fury that year.
The impact on sea life was so catastrophic that it created a dead zone — an area of the gulf devoid of oxygen and sea life — that stretched from New Port Richey south to Sarasota, even reaching patches off Fort Myers.
The algal bloom thoroughly decimated everything in sight that year. It killed everything from bait fish and crabs to rays and dolphins. The final death toll included thousands of fish and birds that fed on infected animals.
Red Tide was the leading cause of death of the endangered manatee that year, killing 93. It also slew more than a hundred sea turtles.
Tarpon Springs sponger Jeff Love, the owner of Rock Island Sponge Co., told the then-St. Petersburg Times in 2005 that the Red Tide snuffed out everything it touched.
"Every plant life, every vertebrate, everything on that bottom is dead," he said. "It's bare rock — and it was the lushest area we had."
From June to September in 2005, Pinellas County alone picked up 732 tons of dead sea animals from its coastline. That's nearly 1.5 million pounds of rotting marine flesh. Local governments had to pay overtime and hire more workers to remove the reeking carcasses.
As the algae remained trapped in lower ocean currents, massive decay squeezed the oxygen from the water. The water smelled like rotten eggs. The silver jewelry divers wore turned black.
The dead zone grew to about 2,000 square-miles. Even light struggled to penetrate the algae.
It stayed that way until Hurricane Katrina passed through the gulf in August 2005 and whipped up the ocean enough to restore some oxygen. Not even a Category 5 storm could destroy the Red Tide.
But Katrina did start to dissipate it. The bloom finally disappeared by February 2006.
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Genthner remembers that time he went scuba diving back in 2005.
As he descended 45 feet into familiar waters off of Longboat Pass, something wasn't right. The water seemed colder and darker than usual.
The experienced diver looked around, trying to pinpoint the problem. He soon noticed the usually crystal blue waters were black. Once colorful corals were now dull. Beneath him, the usually clear sand was packed with carcasses.
"I was swimming through a morgue," said Genthner this week. He was credited with being the first to report his findings to state officials in 2005.
He spotted a flounder lying on the sea floor. He poked it to check if it was alive, only to have his finger plunge through the rotting fish. He also found a dead sea urchin surrounded by its own fallen spines.
Genthner, now 59, said diving into the dead zone was one of the most devastating experiences of his life. Everything about the Red Tide of 2005 was challenging, he said.
His charter boats, which took tourists into the gulf and Tampa Bay, lost business. His average take back then was about $10,000 a month every August, September and October. In 2005, he made less than $1,500 in all three months.
This year, he plans to escape the beating. He found about 900 dead fish killed by the latest outbreak floating by his boat Saturday morning, then booked a plane ticket to New York.
He'll stay there for a week, then head to Spain for six months to work on his back-up plan: his mountain climbing company.
Said Genthner: "The Red Tide will put you out of business if you don't have alternatives."
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It's hard to calculate how much money Tampa Bay tourism lost in 2005.
The Pinellas tourism agency estimated then that Red Tide could have cost the county's tourism industry alone up to $240 million in one year.
Pinellas hotels reported 13,000 fewer visitors from July to September in 2005, the agency reported then, compared to the same period in 2004.
TradeWinds Island Grand Resort President and COO Keith Overton has worked at the St. Pete Beach resort for 23 years. He said business fell off a cliff in 2005.
"We were in a state of panic," he said. "At one point we were having more cancellations than bookings."
He's seen far too many algal blooms in the past two decades, but 2005 was "by far the worst." Dead fish washed up onto the resort's beach. They had to put up warning signs to stay out of the water.
From what he's seen in the media, Overton fears this outbreak could be even more devastating.
"I'm not physically there to see it," he said, "but from the videos and photos I've seen, this one looks worse."
Bruno Falkenstein, who owns St. Pete Beach's Hurricane restaurant with his brother, told the Times in 2005 that they lost 40 to 60 percent of their usual daily business during the outbreak. The smell, the newspaper reported then, could make people sick as soon as they stepped out of their cars.
His brother, Rick Falkenstein, a St. Pete Beach city commissioner, said this week that he wouldn't be surprised if this year's Red Tide enacts a similar toll at the Hurricane — and every other beach business:
"I could absolutely see that happening again."
Contact Jimena Tavel at email@example.com. Follow @taveljimena.