Armed with stainless steel scythes, they swim in low tide from rock to rock cutting down codium seaweed and kombu kelp, which they gather up in bags.
The trio -- 35-year-old marine scientist Alberto Sanchez, his sister Maria and his friend, 33-year-old biologist Sergio Baamonde -- carry the sea greens by foot to their car, parked at the top of nearby cliffs.
Then they transport the algae to a processing factory set up by the two friends in the Galician sea port of Ortigueira, northern Spain.
"It is tough but we are very motivated," said Baamonde, who joined up with Sanchez in April 2012 to launch into the seaweed business, with other prospects scarce in a country hit by an economic crisis that has left one in four people out of work.
They have established a company, Ardora Sea Preserves, to sell edible seaweed, an industry that took root in the Galicia region in the 1980s.
In 2012, sales of ecological seaweed and related foods in Galicia amounted to €3.8 million ($5 million), according to the region's maritime and environmental minister, Rosa Quintana.
Baamonde worked at a laboratory in La Coruna University until "they cut the grant". From 2007 to 2009 he worked as a consultant on on seaweed farming to Galician fisheries associations as part off a regional government programme.
"Then the economic crisis hit and there was no money for the programme," said Baamonde, who found other jobs for a short period before entering into the seaweed business with his friend.
"There is a gap in the market right now in Galicia for this type of gourmet seaweed product and we are trying to fill it," said Sanchez, who worked at a biomedical research centre in Barcelona before launching the venture.
"It took us a year to find the financing," said Sanchez, sitting in a small office at their factory, which has been running since the start of the year at an industrial park in Ortigueira.
The young entrepreneurs invested 300,000 euros, which they raised from relatives, loans and a small state subsidy which allowed them to buy the land for the factory, which prepares the seaweed for sale.
"We want a product that differentiates us in terms of quality, the choice of raw material and the way we prepare it," Sanchez said, stressing the ecological nature of their seaweed product when compared to that of their larger competitors.
Instead of using machinery, much of the seaweed preparation such as washing is done by hand.
Baamonde, Sanchez and his sister Maria do everything from harvesting to preparation to sales of the seaweed -- canned, fresh or dried -- as well as finding new customers.
Among their customers are chefs including Javier Olleros, who has a Michelin star, and Daniel Lopez, chef at the "O Camino do Ingles" restaurant in the city of Ferrol.
"You can achieve flavours that people don't expect," Lopez said as he prepared a dish of hake wrapped in sea lettuce and marinated tuna garnished with codium seaweed while chatting with Baamonde about ways of preparing the algae.
Baamonde and Sanchez are keen to pursue the scientific side of their business, too, by seeking new environmentally friendly ways to process and grow seaweed.
"Our plan is to invest a lot in research and development and we have a lot of ideas," said Baamonde.
"Seaweed is a seasonal product so for part of the year we won't have any work," added Sanchez, adding that they are considering filling the gap by cultivating mushrooms in autumn.
"In the long term we want to work with other maritime produce such as sea urchins but for the moment that is just a plan," he said.