As part of “Take Dad to ‘Dunkirk’ this weekend, I caught the film a second time. I rarely have time to do that, but period pieces/WWII movies and films about boats are kind of my thing. OK, “things.”

One element I fixated on second time around was how writer-director Christoper Nolan didn’t alter the design of the boats to suit filming purposes. Thus, a shroud (cable) holding up a mast on “Moonstone” gets in Oscar-winner Mark Rylance’s face for a few shots.

Another thing I fixated on was the inspiration for this fictional part of the story. “Moonstone’s” story appears to be close to that of “Sundowner,” owned by Charles Lightoller, a former “Titanic” officer, sailed by that owner, his son and a friend of his son to the beach that late spring of 1940. Their story is altered for the movie –the names and backgrounds changed to heighten the pathos and the drama — in a very touching way.

Here’s “Sundowner.” Ran across that photo on Wikipedia.

The boat used in the movie was not an actual Dunkirk “little ship,” but an antique 43 footer — “Revlis.” That name, by the way, is “Silver” spelled backwards. The wooden motor-sailor seems even smaller in the movie, and yes, she was used by the Navy during WWII — just not at Dunkirk. Thus, renting her and recreating studio interiors of her involved less risk to an actual “Little Ship.” Film crews can be rough on historic objects and locations.

Another candidate for “Moonstone” inspiration might be a much smaller and thus not-camera-crew-ready vessel, the famous “Little Anne,” captained for part of the evacuation by the author of the first authoritative book on the evacuation, A.D. Divine. It’s a still-surviving 30 footer, similar lines to “Moonstone,” and was auctioned off a few years ago, having been restored in time for the 70th anniversary sail over. It’s a dead ringer for “Moonstone” in terms of cabin/mast/aft tiller design.

\

Updated: 2018 saw the re-issue of A.D. Divine’s Royal Navy approved 1944 book “Dunkirk.” He was an embedded freelance journalist and eyewitness to the nine days of frantic, blood-soaked evacuation, and his book is a fairly thorough account of the vessels and actions and conditions of the evacuation. He based it on captain’s logs and their reports to the Admiralty, detailing each day’s trip, the difficulties encountered, etc. I highly recommend it.

In relating Lightoller’s logs/reports to the Admiralty about “Sundowner” and his work during the evac, the only thing about “Sundowner’s” work during this period that doesn’t fit “Moonstone” is the fact Lightoller was on a much bigger 60 foot boat.

Like the unnamed skipper played by Rylance in the film, Lightoller lost a son in the RAF during the early weeks of the war, a bomber pilot who told his Dad what to look out for in a dive bombing and strafing (as related in the film). Lightoller plucked survivors of sinkings out of mid-Channel, as in the movie. Divine’s book removes any doubt, it is “Lightoller” who inspired Rylance’s character.

Nolan could not acknowledge that and still take the historical liberties he did, and mentioning “Titanic” would have hijacked that third of the movie.

In terms of historical accuracy, let’s focus on the film’s harrowing death toll. There is no actual casualty count from the evacuation. But thousands died. That is lost in much of the “Miracle of Dunkirk” historical spin associated with the withdrawal. Over 200 British and Allied ships and boats were sunk during the battle, a staggering number. We’d remember D-Day for much darker reasons had the Allies suffered similar losses in attempting to storm back into France four years later.

Among those lost — HMS Wakeful, a destroyer whose motto was “Si dormiam capiar,” “If I sleep, they will catch me.” “Wakeful” went down with 640 evacuated soldiers on board. One survived. That sinking — and others like it — figure into the film.

I could not find an account of a U-Boat sinking an Allied ship by torpedo, something the film suggests. But German E-Boats, their motor-torpedo boats that patrolled the Channel, wreaked havoc on the evacuation. A torpedo in the dark is just as deadly coming from an E-Boat as from a U-Boat.

I was also struck, on second viewing, by the groaning, rattling nature of the Spitfire Tom Hardy’s pilot flies. It stands out because that’s all we have to focus on in Nolan’s brilliantly minimalist aerial scenes. Lovely sound detail, which anyone who has ever owned a vintage British roadster will recognize as British “that’ll do” clever but under-built engineering. Nimble, quick, graceful — not built for comfort or quiet. Did they leak oil, too? Just curious.