The invasion happens each year. They descend on the waters off Martha's Vineyard. They come from places like Boston and New York: tourists! But the onslaught came early in 1974, and it wasn’t the usual seasonal crowd. This time they came by the hundreds… from Hollywood.

Twenty-six-year-old director Steven Spielberg had convinced his reluctant studio heads that he had to film his new picture, "Jaws," on Martha’s Vineyard, and in the open Atlantic waters off its coast.

Shooting began on May 2. It was nightmare from the start.

It quickly dawned on Spielberg that he might have bitten off more than even a great white shark could chew. Here he is just four days into filming.

Scheduled to shoot for 55 days with a budget of about $3 million, it would take more than six months and balloon to a cost of $9 million.

If shooting off in the waters off Martha’s Vineyard presented Spielberg with problems, it also provided him a critical solution: veteran seaman Lynn Murphy and his wife Susan.

"They hired a boat with no man and then they put one of their — from Hollywood or wherever he was from —aboard to steer it and run it and tow things," Murphy said. "And he couldn’t do it. He thought he was going to do it overnight, I guess. The man wasn’t a boat handler."

The "things" that Murphy is talking about is nothing less than Jaws itself. Not only did Murphy help redesign the multiple failing mechanical sharks used in the film, but every time you see a fin carving through the water, or the shark — teeth gleaming, lunging toward a swimmer or a vessel — Lynn and Susan Murphy are in their boat, somewhere just out of the frame, making the beast move.

"My favorite shot that we did is the scene where the Orca has sunk, Roy Scheider is hanging on the mast with a gun and the shark is swimming up towards him," Lynn Murphy said. "That was our masterful shot, that is the best thing we did in the whole movie."

Spielberg’s gamble paid off. With the help of the Murphys and countless other islanders who served as extras, consultants, and production crew, "Jaws" would go on to succeed beyond anyone’s wildest dreams. The film grossed nearly half a billion dollars at the box office, established the template for the Hollywood summer blockbuster and launched Spielberg into superstardom.

Forty years later, "Jaws" is still felt on the island, says Martha’s Vineyard Chamber of Commerce head Nancy Gardella.

"Because so much of the island is protected and will never be developed, there is scenery that remains the same almost 40 years after "Jaws was filmed," Gardella said.

This makes it a unique, must-see destination for thousands of "Jaws" super fans, even to this day.

"There is annual pilgrimage in August of 'fin-addicts' who come for the outdoor showing of the movie," Gardella said. "There are two restaurants called Sharky's Cantina, one of them has a fantastic 'Jaws' display, and so for fans of the movie, that’s a great stop off."

All this, despite one tiny little fact.

Peter Benchley, author of "Jaws" on Greater Boston in 2004

"We almost never see a shark," Gardella said. "So, that’s pretty funny that Martha’s Vineyard became known for sharks in a place where we almost never see sharks."

Meh. Details.

Martha’s Vineyard, forever preserved in film history as Amity Island in the movie "Jaws," which began shooting there, 40 years ago today.