I know everyone in the movies pays lip service to how critical the screenwriter is to the process of filmmaking, but we all know the truth, either because we've seen the dismissive contempt with which the system treats writers or because – as movie fans – we've seen the results that come out of Hollywood and wondered whether barely literate five year olds are getting jobs writing scripts these days.

But here's an example of where a story goes naturally from point A to point B in linear fashion but whose structure has been reconstituted into something elegant and simple that works beautifully as a dramatic narrative.

I don't know if Tami Oldham wrote the memoir this film is based upon with that structure or whether it came from screenwriters Aaron Kandell, Jordan Kandell and David Branson Smith. But when it came to the denouement of her boyfriend Richard's influence during the ordeal, the suckerpunch twist at the climax pretty much floored me.

If you don't know the story, Oldman and her lover Richard Sharp set off from Southeast Asia bound for the coast of California in the early 80s, sailing right into the heart of Hurricane Raymond after diverting to Hawai'i to try and avoid it.

We meet young twentysomething Tami (Shaelene Woodley) in Tahiti, travelling the world to escape her provincial upbringing in suburban San Diego, possibly running away from something we're never really sure of.

Of course, we actually meet her for the first time in a very different light. The story opens with her waking up, soaking wet, a deep gash in her head, the detritus of the yacht she's in strewn around her and with water up to waist level in the wreckage. Bedraggled, hurt, confused and terrified, Tami realises she's shipwrecked alone, miles from nowhere.

We cut to her life a few weeks earlier, a quiet, self-contained young woman doing odd jobs throughout the tourist shipyards of Southeast Asia and seeming like she's finding herself in her travels. Then we cut back to her trying to calm down in the wreck of the yacht, attaching the pump to get rid of the water, trying the radio, scanning the horizon and trying not to panic.

Then it's back to her life as a soulful traveller, meeting a young man when he puts his yacht into the harbour where she works. Her and Richard (Sam Claflin) catch each others' eye immediately and she's swept off her feet in a series of beautiful locales, restaurants, markets and hotel rooms as they fall in love.

The story crisscrosses back and forth between Richard and Tami's courtship and her desperation to try and raise help from the high seas. Not long after she awakens she spies Richard clinging to a lifeboat halfway to the horizon, apparently alive.

Scared but resourceful, Tami knows enough about sailing and oceancraft to tie herself on and swim out to retrieve him, somehow getting him back on board despite his torn open leg and blackened ribs. Their food and water are desperately low but with Richard's help and encouragement she does her best to figure out where they are and how they're going to reach land before they sink or starve. She even dives below with a spear gun and hunt for fish before they run out of food at his insistence despite being a strict vegetarian, a task she takes to with frustration but eventual dedication.

Back on land, with her life an idyll, a shadow is cast when a couple of local friends of Richard's give him an offer too good to refuse – sail their ship back to San Diego (the very town Tami has fled from), and they'll pay enough to set the pair up for world travels together for years to come.

For Tami it's bittersweet. She hasn't got the roving out of her system and the last thing she wants is to go back home too early. But after some soul searching she agrees to go with him, and it's the trip that will deliver them to their ultimate fate with a monstrous ocean storm.

The deft storytelling structure goes a long way, and the visuals effortlessly do the rest. Director Baltasar Kormákur has proven how talented he is with expansive scope, disaster-scale action and VFX with Everest, and with his DP Robert Richardson there's a beautiful juxtaposition between the intimate love story at the centre and the endless ocean around.

From extreme long shots of the half-destroyed yacht and the sea stretching in every direction to the heart-pounding sequence in the storm when Richard and Tami confront a wave as tall as a skyscraper, it would have been something to behold on the big screen. A hallucination Tami has of a giant container coalescing out of the fog at night and disappearing into the gloom just as quickly is particularly haunting and beautiful.

Special mention also has to go to the make-up and costuming, which the performances very much sell – Woodley in particular. For most of the movie Claflin just has to lie there weakly, making the story very much Tami's. And Woodley, with her peeling lips, fatigued slump and a series of cobbled together outfits to protect her against the elements, is wonderful in the role. She's certainly a pretty girl but there's an old soul quality about her that makes her paradoxically reserved but telegraphs Tami's anguish brilliantly.