“The Surface” opens Friday at Point Cinemas. PG-13, 1:26, two and a half stars out of four. The film’s director of photography and co-producer, Jimmy Sammarco, will be doing a Q&A after the 7 p.m. show on Saturday, May 16.

First off, all hail Gil Cates, Jr’s “The Surface” for not only shooting in Milwaukee, but shooting the hell out of Milwaukee. The city looks great in the film, from the shots of Milwaukee’s gorgeous lakefront to the vast blue waters of Lake Michigan, which the film makes look both soothing and ominous.

Cates and screenwriter-producer Josh Gendelman plunk two intriguing characters (played by two strong character actors) in the middle of this blue and watches what happens. “The Surface” is at its best, both as a suspense drama and as a character study, when it keeps things that simple and elemental.

Sean Astin (“Lord of the Rings”) plays Mitch, and in the opening 15 minutes or so, we never see him speak, much like Robert Redford in “All Is Lost.” Instead, we watch him as he patiently loads up his rickety motorboat (including a few mysterious-looking bottles), takes it down to the marina and launches it into Lake Michigan. Something about the grimness on Mitch’s face suggests that this is not a pleasure cruise.

Whatever Mitch’s plans are, they become thwarted when he comes across the wreckage of a small plane in the middle of the lake. Clinging to a half-submerged wing is Kelly (Chris Mulkey of “Twin Peaks”), an injured pilot suffering severe burns and a broken arm. Mitch hauls him into the boat, along with a mysterious backpack that Kelly is guarding.

It turns out both men have secrets, and as they wait for help (and watch the water slowly rise in the punctured boat), Mitch and Kelly start drawing each other out, sharing their stories. Ultimately, “The Surface” is a floating two-character play, and the two actors have great chemistry together.

Mitch is reeling from a series of personal tragedies, but Astin satisfyingly underplays his grief. He finds an excellent foil in Mulkey’s Kelly, a gruff, gravel-voiced charter pilot with his own crosses to bear. Mulkey has more to do here, especially as he has to play injured, and he gives Kelly a hard-won wisdom as well as a caustic wit that lightens the often heavy subject matter of the film.

If “The Surface” had just kept the camera on these two men, it would have been stronger. Unfortunately, Cates and Gendelman decide to include a lot of intrusive, clunky flashbacks that sap “The Surface” of its energy. We don’t need to see shots of Kelly arguing with his wife over money — we can see his plight written across his weatherbeaten face.

“The Surface” has such fine performances in it from Mulkey and Astin that you wish the filmmakers had trusted them more, letting them bring the film back to shore on their own.