There can be few more pleasurable ways to acquire a spot of Latin than wading through cool, clear Atlantic waves off a southwest Kerry beach.

In checked shirt, shorts and neoprene bootees, our teacher has all the knowledge and enthusiasm of a David Attenborough and all the wide-eyed verbosity of inventor Doc Brown in Back to the Future as he wields a knife below the waterline.

"Fucus vesiculosus: that's bladderwrack," John Fitzgerald says. "Ulva lactuca: sea lettuce. Fucus serratus: now there's a lovely one for your bath."

"And here's the wonderful Saccharina lattissima, or sugar kelp," he adds, as he stoops down, cuts a piece and fires it in our direction. "Doesn't it look just like a piece of crocodile skin?"

To say Fitzgerald is passionate about his subject is an understatement. He is originally from Cork and is a former commercial fisherman. He and his wife, Kerryann, have been running seaweed-foraging workshops in Kerry since 2009.

“The Vikings knew a thing or two about the nutritional qualities of some of the 500-plus species on our coastline,” he has explained with a slideshow at the Blind Piper bar in Caherdaniel, before taking us to the appropriately named White Strand just south of Castlecove.

There are early written references to monks harvesting dillisk or dulse (Palmaria palmata) on places such as Skellig Michael just up the coast, he says. Both St Brendan and the Vikings are believed to have carried dillisk on long voyages; it is "packed with vitamins, minerals and trace elements", including vitamin C, and so protects against scurvy.

Sea vegetables

Seaweed – or sea vegetable – is the collective name given to macroscopic algae. Irish botanist William Henry Harvey divided it empirically into three groups – green, brown and red algae – in the 1800s. Harvey's categorisation reflected the fact that the algae evolved to photosynthesise at different depths, Fitgerald says. As with all good plants, it derives its energy from the photosynthesising sun.

“The weeds all have chlorophyll, but their different colours come from dominating protein pigments: brown in the case of brown algae, and red in the case of their red counterparts,” he says.

Two American marine biologists and their Canadian companion among our group of 12 are lapping this up, while restaurateurs Arthur and Lydia Little of Greenes restaurant in Cork cannot believe their good fortune. Arthur, bag in hand, is scooping up samples of the fresh weed, even as Fitzgerald forages. The rest of us nibble, having been assured that "what's fresh is fine".

"Now look at this," Fitzgerald says, commanding attention as he holds up another specimen. "This is sleabhac or Porphyra, which is best known as Nori in Japan, China and Korea, where it is farmed . . . and is probably the most highly consumed seaweed on the planet."

It comprises up to 37 per cent protein, was once routinely boiled and eaten like spinach in the late 18th and early 19th centuries, and even gave its name to a nearby townland. Daniel O’Connell “probably had sleabhac gach aon lá”, for it was a staple during Lent when meat was banned and fish was scarce.

"Seaweeds are little factories for producing Omega 3 and 6," says Fitzgerald. Our pristine 7,800km coastline is fertile territory for a "sustainable and abundant sea garden" rich in minerals, trace elements, anti-oxidants and easily assimilated nutrients. Seaweeds are virtually fat-free and are fibre-rich, and can contain as much as 10 times the minerals of land plants. Some are well over one-third protein. Sea grass (Ulva intestinalis) has the highest levels of vitamin B12 of any known plant, while the alginates, fucoidans, laminarins, fucoxanthins and phyto-defensive compounds found in other types have been shown to have anti-inflammatory, anti-rheumatic and anti-bacterial properties.

Seaweed extracts are used in everything from ice cream to toothpaste. Fitzgerald holds up a kelp rod, better known as a “stipe”. It was once used for potash production, until a French chemist found it was a good source of iodine, he says. When alternatives sources for both were discovered, kelp rods lost their value, but they taste “delicious” if shaved into crisps and pan-fried.

We chew samples of sea spaghetti cut from a rock pool. “Just as good as the spaghetti you buy.” Also good chopped up and added as an ingredient in carrot cake.

There's nothing new about all this, he says: think of how the Aran islanders learned to fertilise sand and rock with marine algae. Carrageen moss (Chondrus crispus) was a regular in cooking, and an effective remedy for flu. Seaweed baths draw out oils, gels and minerals to nourish and replenish skin and hair.

But although it is common knowledge that a "sea veg a day keeps health professionals away", there came a time in our recent history when we turned our back on coastal resources, content to let a little-known State company named Arramara Teo ship out hand-harvested and dried quantities of the brown algae named "an feamann buí" (Ascophyllum nodosum) to feed the alginate industry.

Marine researchers such as Prof Michael Guiry of NUI Galway's Martin Ryan Institute had long maintained that the potential of the resource was not being tapped, Fitzgerald says, and a report by a national seaweed forum based at NUIG in 2000 highlighted "economic and employment opportunities".

All that seems academic now, for Arramara has been sold to Canadian seaweed multinational Acadian Seaplants for an undisclosed sum. The new owner has applied for harvest-licensing rights on a stretch of coast from Clare to north Mayo.

“When it comes to the marine, we’ve a pretty good record of selling off the family silver, or even giving it away,” Fitzgerald says. “Acadian is a world leader in research and development, and knows what it is doing. Maybe we should have tried to poach a few of its bright young scientists to build up our own expertise here.”

Clambering over rocks, he leads us to another part of the beach where there is a particular treasure. The fiery taste of pepper dulse (Osmundea pinnatifida) wards off grazers such as limpets.

“This is the truffle of the ocean,” Fitzgerald says. A Scottish company sells it in concentrate for vast sums per kilogram, he adds. His partner, Kerryann, dries it and sells it in jars as a tasty herb.

A 10-course banquet

We’ve worked up a good appetite, and the tide has turned. Time to leave the strand and travel back in convoy to the Blind Piper, where a banquet awaits. Kerryann has prepared a 10-course repast, using various seaweeds, along with elderflower and sugar kelp “champagne”.

To start, she explains, there is nettle and channel wrack (Pelvetia canaliculata) soup, followed by pea hummus with sea grass, wild garlic pesto with sea lettuce, and cheesy twists marinaded with sea spaghetti, chilli and ginger.

There is kimchi with kelp relish; a labna or yoghurt cheese with sleabhac and spice; dillisk crisps with chilli and lemon; and two types of damper bread – one with dillisk and fennel, and one with sleabhac and herb mix. There are also kelp cookies; sea brittle with dillisk and sea lettuce; Irish moss pudding made with Carrageen; and a black cherry and lavender coulis or thick sauce, also with Carrageen.

As Kerryann moves between kitchen and table, Fitzgerald serves the elderflower champagne and chats away to the group. Many of the recipes used by the couple come from Prannie Rhatigan's Irish Seaweed Kitchen cookbook.

Food tourism is “such a growth area”, Fitzgerald says, and Fáilte Ireland’s Wild Atlantic Way driving route has given it extra focus. When he began his foraging workshops, many of the groups comprised transition year students, scouts and adult-education classes.

“Increasingly, I am finding people who are seriously interested in food, and who find this to be a bit of an offbeat way to spend a morning or afternoon.”

Fitzgerald, a licensed skipper, also leads historical tours. The following day, he is due to bring a flotilla of local boats out around Scarriff island in Kenmare bay to commemorate the 352nd anniversary of the beheading of a local hero, Fr Francis O’Sullivan, also known as the Red Monk.

Sun-kissed and sated, some of the group begin to disperse and offer to pay. Fitzgerald presents each with a seaweed bath pack, along with an edible seaweed identity chart. As he collects payments, he takes out a wallet made of salmon skin, quipping that former Soviet Union statesman Mikhail Gorbachev and his daughter, Irina, were once presented with same.

"It was when I was at the University of Northampton that I began to develop the idea, and founded the Irish Salmon Skin Leather Company," he says. "Salmon skin is five times the tensile strength of bovine leather, because the fish has to survive that journey up to the Greenland straits and back."

Foraging was never so much fun . . .

• For inspiration to plan your own Lesser Spotted Irish break, visit discoverireland.ie

GO FORAGE

Atlantic Irish Seaweed runs tours and workshops tailored to beginners and the seaweed-savvy alike, and from schoolchildren to tourists. Food offerings range from four delicious tastings to a 12-course sea vegetable feast complete with seaweed champagne. Contact John Fitzgerald via atlanticirishseaweed.com or on 086-1062110.