He doesn’t remember how it started. Somewhere between the first cruise and the 75th, it just became habit.

Joe Johnson and his wife, Phyllis, would polish off a bottle of wine at dinner, slip a note inside, pop the cork back in and pitch it overboard — eventually throwing 100 bottles, give or take, spinning into the waves.

At first, Johnson wrote the messages by hand. But, after so many trips, it seemed easier to type them up. The words were almost always the same.

“Your curiosity has paid off,” the note would begin. It’d go on to explain how Johnson had been tossing bottles just like this one into oceans all over the world — off the icy coast of Alaska, into the turquoise waters of the China Sea, near the sun-soaked beaches of the Bahamas. Each letter carried the same hope: that someone, somewhere, might find it and send the note back. For their trouble, Johnson promised, there’d be a $20 cash reward.

But that was years ago, a pastime long blurred in Johnson’s memory as he settled into quieter days at a retirement community in Timonium. Then, last week, the phone rang.

It was a reporter from Australia, with news: One of Johnson’s bottles — one he’d tossed off a cruise ship along the coast of Brazil 16 years ago — had just washed ashore. Somehow, it had made a more than 10,000-mile journey across half the world to a beach in Victoria, a southeastern coastal state.

The call left Johnson marveling. How had the bottle made it so far? How had it escaped sharks, survived crashing waves and avoided sinking to the ocean floor?

The answers lie in the flow of ocean currents, the snug seal of a cork — and a good dose of luck, according to University of Maryland professor James Carton, who studies oceanography.

“If you were to tell me a bottle was dropped off Brazil and ends up in Equatorial Guinea or Africa, that’d be easy to do, piece of cake,” said Carton. But to make it all the way to the eastern coast of Australia, Carton said, “that’s very unusual.” Though not impossible.

A journey of more than 10,000 miles

This map shows how the ocean currents played a role in the bottle’s journey from Brazil to Australia.

Ocean currents work like invisible highways, guiding the water — and whatever floats in it — in specific directions. To make it that far, Carton said, the bottle had to travel down the coast of Brazil, sweep around Antarctica, catch a ride on the South Indian Ocean current, and finally drift from one end of Australia to the other.

And that’s not even counting the obstacles that it had to dodge along the way. Sixteen years is a long time to stay afloat, Carton said. For the bottle to keep riding the surface, it needed to be tightly sealed — surprising, given that it was closed with nothing more than a cork. It also had to avoid crashing into boats, getting snagged by sea life or smashing into land.

If Carton had to put a number on it, he’d guess the odds of this happening are about 1 in 1,000. That makes Johnson’s luck exceptional — it only took him 100 tries.

“This is a crazy story,” Carton said.

All of Australia seemed to think so, too. It started with a post in The Peterborough Press, a local Facebook group, where someone shared how they’d found a green wine bottle during a morning walk on the beach. Inside was a note from a man in Maryland. The story took off, landing on Australian TV, radio and newspapers.

Back in Baltimore County, retired lawyer Johnson found himself juggling press interviews and overwhelmed by emails from around the world. It got so out of hand, he said, he stopped checking his inbox altogether.

Some of the messages were kind. Others? “Unscrupulous,” Johnson said — people trying to take advantage of an old man, even if just for $20.

At 89, he doesn’t see any more cruises in his future — or any new messages in a bottle. That was always something he did with Phyllis, who passed away in January. Without her, it’d be too hard.

Still, the adventure may not be over just yet.

“It’s conceivable that another bottle may turn up one day,” he said. But until then? “I’ll be glad when this all subsides and people stop sending me emails.”