-By Frank Lovece

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At 77 minutes, this documentary about a divorced dad's five-month boat journey with his three grown children and others through the Northwest Passage is engaging and exotic and frustratingly truncated. A sometimes nightmarish dream journey through the storied and treacherous Arctic sea route, it records the interpersonal tensions of a family cramped inside a small vessel in unforgiving waters and unfamiliar landscapes—for five months, did we mention that? It's a sign of both its intrinsic power and its imbalanced craftsmanship that you want this film to be longer and to answer many unasked questions. Filmmaker Sprague Theobald generally does news segments and documentary shorts, which helps explains his awkwardness with the longer form. And for all that, The Other Side of the Ice is mesmerizing.

And Theobold may be craftier a filmmaker than one thinks, if you consider this a teaser for his 2012 book, The Other Side of the Ice: One Family's Treacherous Journey Negotiating the Northwest Passage, which presumably addresses some of the questions the movie raises.

In early 2008, Sully Sullenberger doppelganger Theobold began planning his 8,500-mile trip from Newport, R.I., to Seattle, Wash., on a 57-foot powerboat, the M/V (Motor Vessel) Bagan, which he outfitted as a floating production facility. After a divorce that to varying degrees scarred his son and his two stepchildren, he eventually constructed a good relationship with Sefton Theobold, at this point a 22-year-old college student, and Dominique Tanton, his stepdaugher. Stepson Chauncey Tanton, the eldest, however, admits to having been estranged for almost 18 years before hearing about this expedition. Summing up the film's thesis, Sprague says, "I didn't set out to do this trip with family… Just slowly family started joining… This extended family that has not been physically together in over 15 years is now together doing this trip. Are the kids gonna walk off the boat and say that was the worst five months I have ever experienced?" Or, for that matter, not die?

Sprague, Sefton, Dominique and her boyfriend, experienced mariner Clint Bolton, depart Newport on June 16, 2009, picking up professional cinematographer Ullie Bonnekamp in Halifax, Nova Scotia, four days later. But tensions between him and the crew mount, particularly with Clint—who's kind of a tool who barks at his girlfriend till she's in tears. Ullie departs when they reach Sisimiut, Greenland, on July 20, and underwater photographer Greg DeAscentis, with whom Sprague had worked before, come on, as does Chauncey.

Long story short, their planned route gets blocked by ice, in which they become stuck for about a week in early to mid-August, and they head south to take one of the more circuitous routes between Somerset and Prince of Wales Islands, to the Gjoa Haven hamlet on King William Island, then through the straits south of Victoria Island to the Beaufort Sea, where the Northwest Passage ends. It sounds a marvelous adventure.

The only problem is, we don't see most of it, and only learn the bulk of the above through a map on Theobald's official website. In what appears to be a discrepancy—honest, I'm sure, but still—the online map shows the Bagan reaching the Inuit town of Resolute. Yet, according to the film, they never got closer than about two miles away before ice forced them to head south. There's no mention of those other stops they made—extreme outposts that would have been fascinating to see and quickly visit onscreen. The next we know, the Passage is suddenly behind them. There's still a long way to go, along the coast of Alaska and through the Bering Strait, but the film rushes through all that.

What few vistas we do see are staggering, and the crew's reactions to such fauna as polar bears are probably the same as ours—roughly, "Holy crap! Look! A polar bear! Awesome!" That's pretty endearing, as are Theobald's frequent inclusions of what would normally be outtakes before and after a shot. ("We rolling?")

The film often uses the confessional, speak-to-the-camera format of reality shows, but in this far less artificial context, and minus prompting producers, it works on a gut level. And when they reach the grave markers at Beechey Island, where the 19th-century Franklin Expedition perished, it's easy to understand Sprague's feeling of "desperation…like we were desecrating a cemetery. It was all around the Northwest Passage, that feeling of something's wrong." Appropriately sepulchral music thrums with electronic tension that would seem to well echo that feeling of utter and deadly desolation. In his apartment in 2012, Sprague reflects, "I feel bad about the trip [because] I haven't had enough distance to stand back and realize what a powerful trip it was."

And there's no question this voyage was dangerous. Yet with all the talk of being encased in ice and of options running out, a layman's mind starts to wonder why, if they had satellite phones and radio communication, they couldn't call for help if necessary—surely the Canadian Air Force could do a helicopter rescue.

That's one of those unanswered questions that now make me want to buy the book. Well played, Theobald, well played!