Ahoy, mateys. Stow the popcorn, secure your rigging and fasten your life vests. The surf is up.

As “The Lighthouse” begins, we meet our actors as they step ashore to tend to an ancient lighthouse that perches on a large rock in the middle of a very large, turbulent body of water on the coast of Maine somewhere in the 19th century (shot in Nova Scotia). They are here for one month to relieve the old crew and and keep the light going.

Behold Thomas Wake (Willem Dafoe) as a crusty, aging, flatulent, old sailor, who talks like a stock movie pirate with what I’m told is a Maine accent, and who has taken up mending old lighthouses.

Wake is in charge of his apprentice, the handsome Ephraim Winslow (a vastly improved Robert Pattinson), who used to be a lumberman, but did something bad and is now looking to withdraw from the cold woods to the even colder east coast. There, he will paint and scrape and shovel coal to keep the light ablaze, while old Tom sits in his chair puffing on his clay pipe and boring his mate, and us, with his seagoing yarns punctuated by the high and low notes of the persistent foghorn and crashing surf. Get used to it.

Robert Eggers (“The Witch”) shot this film in 35mm black and white, and is viewed by us in the annoying square ratio of those old German vampire movies. It opens this week at Waterville’s Railroad Square Cinema, just in time for Halloween.

But this is Robert Eggers’ film, and he brings no cozy Maine story to soothe you. Eggers is not in the soothing business.

There are a couple of laughs embedded here, but I feel obligated to highlight a few occasions in this film that may disturb the stomachs of those of you have just dined at Buen Apetito next door. Three margaritas, on the other hand, may be beneficial.

You will, in the course of this tenebrous 1 hour and 50 minutes, view the graphic rape of a mermaid (yes, there is a mermaid, Valeriia Karaman) on the hard, cold rocks of the beach. Valeriia has one maniacal laugh and screams, but no lines.

No dogs or horses were harmed in making this film, but a brutal murder of a seagull is shown. Clearly, seagulls are not covered by PETA’s rules.

The last and very graphic lingering shot of a seagull slowly devouring a body, eyes and lips, and feasting on the entrails of a corpse was, for me, the final straw — or seaweed.

Fans of Pattison and Defoe will be happy to learn that both earn gold stars for playing well together and getting along — until they don’t.

Wilson is the best role of Pattison’s career. Not since Orson Welles’ breakdown in “Citizen Kane” has an actor been given such freedom to go full-out bonkers, run amok, destroy the scenery and scare the hell out of us and his co-star.

Defoe, who loves to wallow in the rancid depths of broken men, gets his chance to splatter the camera with blood and spit, and no one since silent star Lon Chaney has done it better.

We can just feel how eager he was to get to work on that rock each day. As the deranged Tom Wake, he redefines “over the top,” and gets to project the madness he missed in his portrayal of Vincent van Gogh.

Writer-director Eggers, clearly a cinema artist, has his many fans, but I’m not going to be one of them.

I should note that “The Lighthouse” got a 100% on Rotten Tomatoes and won the International Federation of Film Critics (Fipresci) Directors’ Fortnight and Critics’ prize at the Cannes Film Festival and will surely be noted at Oscar time. Make of that what you will.

J.P.  Devine, of Waterville, is a former stage and screen actor.