In 2018, Andy McMillan was in a bar in Memphis when he met a man from New Jersey who was, improbably, floating the 2,300-mile length of the Mississippi River from Wisconsin to the Gulf of Mexico in a houseboat.

He was “making his way through the crowd with printouts of news stories about him,” McMillan said.

Less than a month later, McMillan, co-director Tim Grant and their cinematographer Ben Joyner had signed up to film the journey down the river with Kelly Phillips and his pug, Sapphire. They had an inside view of an inspirational story: A man, staring down a fatal cancer diagnosis, choosing to take to the water for his remaining days.

Their feature-length film, “Mississippi River Styx,” which will have its world premiere on Friday at the Big Sky Documentary Film Festival, takes viewers along, posing more questions than answers.

During his trip, Philips met numerous people curious about his story, no shortage of whom seemed eager to help. Besides their desire to aid a person who was dying, there was also the incredible danger of floating the river in a houseboat.

During his months and months on the water, Phillips accumulated a long list of newspaper features and television news stories and a “sense of agency with his own narratives,” according to McMillan.

“There was something more to his story in general,” he said. "It wasn’t this necessarily happy, inspirational bottom-of-the-news-hour story that it was presented as."

Shooting on the water

The filmmakers start the tale at 1,400 miles, and filmed with Phillips a few weeks at a time for around 13 months.

It’s the first documentary for McMillan, a North Carolina native and photographer. Grant is a southern Appalachian director and producer whose first short, “The Aria of Babyface Cauliflower Brown” was tapped for The New York Times Op-Docs.

For logistical reasons, shooting on a rather small vessel, which one experienced riverman compared to a busted-up pontoon boat, posed difficulties. Not just with safety, but shuttle vehicles and other issues.

McMillan and Grant were on board most of the time, and Joyner perhaps 70%. With that many people in a tight craft, trying to get footage without another filmmaker was often tricky.

From a filmmaking standpoint, some scenes plainly display the risks involved in Phillips’ plan. The final section of the river is a major shipping area, populated by massive vessels. A river safety official compares it to riding a bicycle on the interstate. It leads to a scene that’s more dramatic than usual knowing it’s not a movie shoot.

The score was written and performed by saxophonist-composer Joseph Shabason, who played with Destroyer on the synth-laden album “Kaputt,” and with dreamy Americana act The War on Drugs, and his collaborator, the guitarist Thom Gill. Shabason, a multi-instrumentalist, uses effects that can mimic the sound of a horn section. The two performed it live, and sections like one during a rocky and dangerous course on the water project an improvisational, reactive tension.

“Every single time they would send us a cue, it just opened up the movie in a new way,” McMillan said.

People’s perceptions

With his current health situation and family tragedy, people in an area known as “Cancer Alley,” have been affected by it in their own lives and so the story has added weight.

“It’s really a story about perception,” McMillan said. They designed a “daisy chain of narrators that tell the story as we float down the river – they’re not always authoritative, and they’re not always even correct with what they say. It’s always sort of projections onto the story that they’re delivering.” 

Rather than go back and interview people (with one exception), they talked with people that Phillips interacted with as they made their way down the river and he makes frequent stops to churches, bars and diners.

Phillips makes friends easily, and McMillan said he was outgoing and energized by attention. Those who befriended or tried to help him include a retired art teacher, a tugboat captain, a police officer, a river safety official, and more. Some are filmed in an “environmental portrait” fashion, McMillan said, where you get some insights into who they are and the vantage point they stand on. Many of them reside in Venice, a small community that McMillan said is a frequent location for reality TV shoots, and they said they wanted to hear locals’ points of view on the story.

Grant said the varying perspectives added another element to the story.

“There are different versions, and comparing them against each other is really what our movie is about,” he said. “The way Andy says, it’s not a whodunit. The whodunit would give you the answer. Hopefully, by the end of the film, you have a lot of questions that have been asked by the various perspectives on Kelly’s story.”

McMillan said the TV news versions of his story were what they had time to produce, which in a way “fuels his trip down the river and makes him into a minor celebrity.”

As filmmakers, they had much more time and “we ended up becoming much more interested in the subjectivity of these stories.”