The tourists who cram into Chatham, a tidy seaside resort on the Cape Cod peninsula, get their shark fix by watching Jaws, which plays nightly at the Orpheum on Main Street, or perhaps by buying a toy in one of the souvenir “shoppes”.

People seem to love sharks, especially the great whites made infamous by Steven Spielberg in his 1975 film, shot just across the water in Martha’s Vineyard.

Perhaps it’s the fearsome and mysterious glass-dead eyes. Or maybe it’s that line in the film: “You’re gonna need a bigger boat!”

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One such bigger boat – better equipped and funded too – is a blue and white vessel, which the Chatham tourists might just spy anchored off the Monomoy National Wildlife Refuge, an eight-mile spit of sand extending south from the Massachussetts coastal town.

The MV Ocearch, once an Alaskan crabbing vessel, belongs to Chris Fischer, a man his friends describe as a cross between the late French marine documentary-maker and diver Jacques Cousteau and businessman Richard Branson.

“It can’t be even measured, it’s that huge,” Mr Fischer, 44, says of the current mission of his company – also called Ocearch.

That mission is to catch as many Atlantic great whites as possible over three 20-day expeditions this year, fit them with assorted electronic tags that will collect and transmit data about their habits and movements, and then, naturally, let them go. Understatement may not be Mr Fischer’s forte, but what he’s doing is a first in marine science (and rarely witnessed). Much of it is possible thanks to the giant hydraulic pistons that raise a 20ft platform from the ship’s deck and cantilever it over the side to just below the sea’s surface.

Lay a live shark on it and you can do all kinds of things that were previously impossible: not just attach the tags but also draw blood, take biopsies, examine it with ultrasound for pups and even (if it’s a male) express semen from its sex organs, called claspers.

Real great whites, rather than the mechanised kind used by Spielberg, are mythologized in part because scientists still know so little about them.

“For the first time in history we are closing a whole knowledge gap,” Mr Fischer says. “For example, we still don’t where the breeding grounds of the Atlantic great whites are.”

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Spend even one day amid the sailors, scientists and fishermen (and one badly behaved dog named Nixie) on board the Ocearch and the sense of discovery is palpable.

Theories bubble up like gas from the ocean floor. Dr Greg Skomal, senior marine biologist for the state of Massachusetts, almost casually discusses the headline of a new science paper he has just submitted for publication. The consensus now is that a great white has a lifespan of about 20 years; his paper will argue they only mature in their mid-twenties and might live to 70 or more.

“We are pursuing about 12 projects at once,” Dr Skomal explains. “If we combine the results of all the projects, we can get a much bigger picture of the biology of the great white sharks in the Atlantic Ocean, which has been shrouded in mystery. This is all new stuff we are finding out.

“The reproductive cycle is so poorly understood in the Atlantic Ocean. The fact that we are doing an ultrasound on a great white shark is unheard of. I am living in an exciting time when I have moved from cutting up dead sharks to understand them to studying live ones.”

We are here in the shallow Cape Cod waters because it’s where great whites come in summer, drawn by congregations of grey seals on the sand bars and beaches of Monomoy.

At sunrise each day, Fischer and a couple of mates jump into a smaller boat, the Contender, to go great-white fishing. They trail chum on the end of their lines, which are fitted with large circle hooks.

When a shark bites, the Contender will tow it back to the Ocearch and, with a little manhandling from the crew, place it on the barely submerged platform. Get a great white on its side, water its gills constantly, place a shroud over those awful eyes and it will lie still.

Things don’t always work out the way they are meant to. Included in those things the crew doesn’t quite understand is why the great whites are proving so elusive here. So far on this expedition, running all of August, they have only caught two.

When news came from the Contender this Tuesday that they had snagged the second, crew members on the bigger ship punched the air.

Before long, lying on the platform was an immature female about 14ft long and weighing 2,300lb. She turned out to be a thrasher, threatening everyone with her angry tail.

Caught in just nine feet of water close to the beach, the shark – they name her Katherine – nonetheless gets the full treatment for 15 minutes, after which she is returned to the ocean.

A transponder that will send pings to receivers up and down the coast is inserted in her abdominal captivity. A tracking transponder with an aerial that will transmit to satellites whenever she surfaces is fixed to her dorsal fin.

Yet another tag, which will measure things such as depth and water temperature, is also anchored to her body. It will detach next spring, float up and send out its data.

Much excitement on this expedition surrounds Dr Nick Whitney of the Mote Marine Laboratory in Florida and his accelerometer tags. Using the same technology that helps a smartphone detect when you turn it sideways, these tags are designed to record much more than all the other devices.

“The older tags tell you where the shark goes, but this one actually tells us what the shark is doing,” Dr Whitney explains, holding one (they cost about £2,600 apiece) in his palm. “For instance, it tracks tail beats – how hard the shark is beating its tail and how fast it is beating its tail.”

The accelerometer, which is automatically released after 24 to 48 hours, has already shown how quickly the sharks seem to recover after being released by the research team.

Dr Whitney is also learning about how, when they descend, great whites stop all swimming motions, instead seeming almost to glide. “This may be a strategy to save energy but they may even be sleeping on their way to the bottom,” he says. “A power nap.”

Given that Mr Fischer’s main corporate sponsor, the Caterpillar Corporation, is reportedly giving him $2m (£1.3m) per year for three years – he won’t himself confirm this – landing and tagging only three sharks over two expeditions this year is surely disappointing.

If his haul doesn’t improve, the mission cost works out at something more than $600,000 (£385,000) per shark. Yet he and his sponsor are undeterred.

And don’t tell him it’s not worth it for a species that he says may soon be endangered thanks to shark hunters seeking their fins for Chinese cuisine: “Sharks generally are the balance-keepers of the ocean,” he asserts. “They are the lions of the ocean. Yet 200,000 will be finned (and therefore killed) today. The bottom of the ocean is littered with finned sharks – out of sight out of mind. We are literally trading the balance and the future of our oceans for a bowl of soup.”

It does not escape Mr Fischer that without the public’s fascination with sharks – thank you Steven Spielberg – his Ocearch venture would never have attracted sponsors.

Choose a less sexy species and forget all the fancy technology, the very big shark boat (and the media interest too). “No one would care, it would be ridiculous to argue with that,” he concedes.

But the Caterpillar cash is good until the end of 2015. He chose the bulldozer maker because “if I am to have a global impact on the future of the planet I needed a global partner”.

Everyone on board insists that the sharks come first, always. (Journalists are barred from broadcasting images of the hooks that catch them or any blood spilled while they are being fitted with the equipment.)

Yet, this is clearly also an entrepreneurial concern and, for Mr Fischer, there is an element of competition as well – with his French forebear. “Jacques Cousteau had done 27 expeditions when he was done,” he says. “I will have done 25 by the time I am 47.”

The journeys of the tagged sharks can be followed at ocearch.org