All along the bayou, the canal-like waterway that runs for 15 miles beside the road from Chauvin to Cocodrie, the shrimp boats are tied up; with their twin side nets raised vertically, high in the air, they remind you of soldiers surrendering. And they've certainly given up the ghost for the time being.

Right across the Gulf of Mexico, shrimping has come to a halt – thanks to the BP oil spill and its pollution danger – right in the middle of its most profitable season. "My best catch?" says Captain Tate Grossie, "I tell you, I took 11,000lb of shrimp in three-and-a-half days. Filled my hold. Sold it for $20,000. Best day, on my first drag I took 950lb of shrimp. Major part of my income. So," he says, looking out over the marshes, "if I didn't have this, I wouldn't have nuthin'."

"This" being "a vessel of opportunity". BP, fiercely criticised over the catastrophic Deepwater Horizon spill, has gone some way towards mending relations with the people of the Gulf coast – or at least, not damaging them any further – by promptly paying out compensation for loss of earnings to thousands of landbound shrimpers, crabbers and other fishermen, and furthermore, by offering them employment on top of that, doing what they do best: working on the water.

Those who have boats that are suitable for helping in the oil clean-up and coastal protection operations – and by no means everyone does – are invited to offer them as vessels of opportunity, meaning small craft which BP and its contractors will put to use, as and when.

Captain Tate (or as I start to think of him, Cap'*Tate), who is 44 and had been a fisherman all his working life, has no chance of that with his main boat, his pride and joy, the 53ft wooden shrimper Miss Savannah. She's too big for the clean-up operation's needs, and is consequently now moored in the port of West St Mary with her nets reaching for the sky. But he has something else up the sleeve of his captain's sports-shirt: his airboats.

Airboats, in case you don't know, are metal platforms with a large propeller at the back. They are pug-ugly and louder than helicopters but have indisputable advantages: on calm water they can reach 75mph, and they possess such a shallow draught that they can cruise over any inlet, and then move seamlessly on to low-lying land such as marshes.

An abomination, in fact, for an environmentalist or indeed anyone who loves wilderness for its peace and quiet. But in the great upheaval which is the oil spill, threatening the whole Gulf coastline, airboats which can go anywhere quickly are ideal for the sensitive and finicky work of defending the marshlands of coastal Louisiana, and as Tate Grossie had three of them as a sideline to his shrimping, he was asked to help.

He is operating out of the remote harbour of Cocodrie, 85 miles south-west of New Orleans, which for oil spill purposes is Forward Operating Base Cocodrie, and it gives you some idea of the enormous scale of the oil defence and clean-up operation to realise that there are 17 such FOB's along the Gulf coast from Louisiana, through Mississippi and Alabama to Florida, and between them they are sending out 2,600 vessels of opportunity every day.

I hitched a ride on Cap'*Tate's airboat as he took Petty-Officer John Miller, US Coast Guard, out to inspect the clean-up operation. Petty-Officer Miller seems at first an archetypal member of the military, given to frequent grunts of "yessuh" and "nossuh". But then I discover that he too, in this great upheaval, is not what he seems; he is actually a reservist who has been recalled to the colours, and in civilian life is a Professor of Early American Literature, and if you give him half a chance he will switch out of grunt mode and murmur: "Of course, Emerson was attempting to establish an indigenous American tradition, but he was greatly indebted to European Romantics such as Coleridge and Schiller."

Sunscreened, sunhatted, earmuffed and water-stocked – it was 93F in the shade and the sun was pitiless – we cruised out of Cocodrie's marina into the truly lovely seascape of flat water and small barrier islands which make up the borders of the Mississippi river delta; then we picked up speed. Having had a Catholic upbringing I am used to guilt, but I was unprepared for the massive guilt cloud which enveloped me when I realised that riding in an airboat, which represents everything I cannot stand, was as exhilarating as skiing.

It took about half an hour to reach the clean-up operation. Our corner of the marshes had been spared the heavy oil which had hit further west, yet there were areas which had been contaminated – or nearly so. The marshes and the low-lying barrier islands had been saved by the defensive booms which had been put in place, both the hard protective booms and the softer white absorbent booms which soak up the oil, and all around the horizon, small craft, the vessels of opportunity, were adjusting them and checking them – some were airboats and others, Cap'*Tate pointed out, were shallow-draughted crabbers.

The booms had restricted the oil to about the first 5ft of marsh grass, which was itself repeatedly being cleaned. Most of the landscape remained pristine.

Watching it all going on, I asked Tate how he felt about BP and he said he wasn't angry. "It just happened, it was just one of those things," he said. Like many local fishermen, he had been paid a $5,000 cheque last month for loss of earnings. There had been no hitches in arranging it; it was settled over the phone and arrived promptly. He was waiting to see what happened this month. By the start of this week, BP had paid out 18,000 individual cheques totalling nearly $49m.

Then it was time to head back to Cocodrie. I said to Petty-Officer Miller that they seemed to be making quite a good job of the clean up operation and he said: "Yessuh."

And I said that it didn't seem too bad in this part of the marshes, and he said: "Nossuh." And then he couldn't help himself and slipped out of grunt mode for a second and back into Professorial and blurted out: "You might say it's a small success story, in its own way."