Sargassum Harvester

Aventura Boats

The CleanCat 42 (12.8m), a sargassum harvester to protect beaches from the floating seaweed, was adapted from an Aventura Boats resort tender.

by Peter Swanson

[A] boatbuilder once lamented to me that he couldn’t screen customers by insisting on a psychiatric evaluation before taking their deposits. He was joking, of course, but the joke was a reminder that dreams and ego wrap themselves around a new boat purchase, often causing stress from head office to factory floor.

Lucas Guessard has found a solution that doesn’t involve a Rorschach test. He builds powercats for commercial cus­tomers, not recreational boaters. He says businesspeople are much better at know­ing what they want, when they need it, and how much they are willing to pay. For them, boat buying is a straight­forward business transaction, shorn of romance. A workboat can be fair, plug­ugly, or something in between, but it is essentially a tool matched to a task.

Guessard, 54, is founder, owner, and chief engineer of Aventura Boats, a company in the Dominican Republic, which over the past decade has grown to be the biggest Caribbean supplier of excursion craft to the region’s tourism industry. Visit any down­island resort and you are likely to see Aventura cats serving as dive boats, ferries, or party platforms. All are built at Guessard’s factory in La Culebra, a village on the country’s North Coast.

Juan Mendoza

Wading through the sargassum at the Dominican Republic’s most important tourism region is Jake Kheel, vice-president of the Grupo Puntacana Foundation, a nonprofit dedicated to sustainable growth and environmental protection.

In 2022 Aventura started building a new and entirely different workboat in response to an insidious economic and environmental crisis: Caribbean beaches are being swamped by sargas­sum, or as we say in English, seaweed.

CleanCat 42 Specifications:

Length: 42′ (12.8m)
Beam: 18’6″ (5.64m)
Draft: 2’4″ (0.73m)
Hull: solid FRP
Deck: Nida-Core sandwich
Bulkheads: foam-core sandwich Weight (empty): 7.5 tons
Air draft: 16′ (4.88m)
Fuel tank: 2 x 99 gal (374.76 l)
Water tank: 30 gal (113.56 l)
Power: (2) Yamaha 250 hp (186.51 kW)
Max speed (empty): 24 knots
Cruising speed: 15 knots
Loaded speed: 10 knots
Range: 200 nm
Max load: 10 tons
Price (est.): $450,000 (with special trailer)

The Curse of Sargassum
Tourism in the Caribbean is a $24 billion industry. In 2019, it accounted for 17% of GDP in the Dominican Republic, whose flagship vacation des­tination is the Punta Cana region on the island’s eastern shore. The tourism percentage of GDP is even higher for many of the smaller Caribbean islands.

Three essential ingredients for the success of a Caribbean resort are sun, sand, and booze. Of those, only sand seems finite; there is only so much beach. Cover the beaches with stinky, rotting, brown seaweed, and we have a problem. That problem is a recur­ring nightmare in Punta Cana and throughout the Caribbean, particu­larly on the eastward and south­facing shores. Cancun has been hard­hit, too. The phenomenon has become so prev­alent for five months of the year that May through September has come to be called “sargassum season.”

Aventura Boats

Lucas Guessard, 54, founder and owner of Aventura Boats in the Dominican Republic, began building boats in the late 1990s under some trees along Luperon harbor with the help of local teenagers he trained. Now, in his modern factory about 10 miles inland, those former teens are foremen of his crew of 40.

As science journalist Ed Yong wrote for The Atlantic in 2019:

“In 2018, as seaweed piled up on beaches throughout the Caribbean, it began to rot. Already stinking and sul­furous, the thick layers began to attract insects and repel tourists. The sea­weed—a type of brown algae called sargassum—had grown in the ocean and washed ashore in unprecedented quantities. It prevented fishers from getting into the water and entangled their nets and propellers. It entangled sea turtles and dolphins, too, fatally preventing them from surfacing for air. It died and sank offshore, smothering seagrass meadows and coral reefs. Bar­bados declared a national emergency.”

Maybe it’s caused by climate change, maybe not. Scientists agree, however, that regular annual sargassum blooms have been exacerbated by nutrient­rich agricultural runoff from the Ama­zon Basin, borne north and westward by ocean currents.

The good news is that sargassum has value. One of its components is alginic acid, which the food industry can use as a thickener and emulsifier. Other components can be employed to make paper or ethanol. It also makes excel­lent fertilizer, and agriculture is an important sector in the Dominican Republic and Mexico. Guessard’s task is to build a tool matched to the task of harvesting sargassum before it gets onto the sandy beaches. Delivered clean, sargassum can be put to whatever good use other clever people devise.

Aventura Boats

An Aventura Arawak 42 passenger- carrying model is at work. This is what Caribbean resort operators want their waters to look like.

There’s another reason for Aventu­ra’s interest in the project. Not only is Guessard a builder, but he is also a customer. Aventura’s subsidiary, the Happy Fish excursion company, takes tourists out on the waters off Punta Cana in three Aventura boats. Two are late­model cats; the third is Guara, the sailing trimaran he built in Brazil 27 years ago. “Day after day, we are trying to make all the guests on board happy, so me and my customers speak the same language,” Guessard said. Plus, ensuring the future of Happy Fish pro­vides a strong incentive to solve Punta Cana’s seaweed dilemma.

Creating a Harvester
Over 20 years of fiberglass boat production, Aventura has settled on three basic models, named from the language of the indigenous people—Warao 31 (9.45m), Macorix 36 (10.97m), and the Arawak 42 (12.8m). The 42 is the platform that Guessard intends to adapt for sargassum work. He is call­ing the new boat the CleanCat 42 SH (sargassum harvester), and work began last February for an April launching.

That’s a quick turnaround for a pro­totype, but Aventura has always been a semi­custom shop, adapting super­structure components to customer needs. Guessard, whose education predates the CAD era, says he still has a knack for “empirical design,” a fancy term for building by eye, and his crew are used to making modifications on the fly. He warns that the end product may not look exactly like the CAD renderings accompanying this article. Guessard expects the CleanCat to price out at $450,000.

The design philosophy for his boats derives from the reality that Guessard is “a sailor in a universe of power­boats.” He designed his hulls around the criteria of fuel efficiency and sea­worthiness—as defined by the capabil­ity to take out passengers even during the moderately rough conditions often found at Caribbean beach resorts. All his boats are designed to embark pas­sengers from a beach.

Aventura Boats / Philippe Kermoal Kerm

Two winches control cables from the cockpit to adjust the aspect of CleanCat’s forward conveyor. A crew of two will operate each boat on its harvesting mission, but the flying bridge and side decks have room for up to a dozen observers. As an eco-tour, Aventura is suggesting taking tourists out during harvesting.

Hull construction is solid fiberglass, averaging 1⁄2″ (13mm) thick below the waterline and about 3⁄8″ (10mm) above, with superstructures in composite sand­wich stiffened by Nida­Core. Plywood is still being used for some bulkheads, but as Aventura gets ready to begin production of third­generation mod­els, Guessard said he plans to replace all wood with Nida­Core or polyester foam coring, as appropriate. Platform­to­hull construction is strengthened by the company’s practice of bonding all furniture and other superstructure components instead of fastening them with screws.

Guessard characterized his hulls as “semi­displacement,” able to achieve 30 knots running empty but sensitive to weight, as cats usually are. Realistically, with recommended dual Yamaha 300s running at 3,450 rpm, the Arawak cruises at 18 knots, making 1.2 nautical miles per gallon, Guessard said, noting that speed and fuel consumption vary depending on prop specifications.

Speed and seaworthiness, it hap­pens, are key factors that match the existing Arawak platform to the task of harvesting. Today, seaweed­gather­ing in the Caribbean is undertaken with pontoon boats topped with heavy machinery originally designed to gather nuisance vegetation in rivers, not open ocean. Some are makeshift and locally sourced, others brilliantly designed and extremely expensive, Guessard said. None are very practical, given the pitch and roll of open­ocean work. “These barges are technological dinosaurs,” he said. “They are essen­tially river barges and not suited for the open waters where they must go to harvest the sargassum.”

Containment barriers are the pri­mary technique for keeping sargassum a reasonable distance from resort beaches long enough for the current generation of harvesters to clear it out. Punta Cana alone has five miles of floating barriers. When harvesting ves­sels don’t work fast enough, the trapped sargassum rots and emits a putrid stench, bad enough to affect quality of life at nearby hotels and rental villas. And while barriers may prevent intact seaweed from piling up on the beach, they don’t prevent the color of normally turquoise water from becoming cloudy brown with decaying slime.

Like most small builders, Guessard wears many hats, but what he really enjoys is an engineering challenge. The CleanCat project is an opportunity to do something entirely different. He collab­orated with other sailors and engineers in France to develop the mechanical sys­tems that will sit between the hulls. His design crew includes Eric Lavit, Alexan­dre Demange, and Philippe Kermoal, who drew the renderings.

Guessard is also motivated by a per­sonal devotion to environmental causes see sidebar, below). He’s not preachy about it, nor is he annoyed when cor­porate actors pay lip service to all things green while doing little, because, he said, at least they are sending the right message. To him, harvesting sargas­sum efficiently is an elegant solution to a problem that’s bigger than diminish­ing resort profits. “If we can make organic fertilizer with the sargassum, we can eliminate some chemical fertil­izer that makes the nitrogen problem in the first place,” he said. Bioenergy is another possible use for harvested sea­weed. Guessard’s sales pitch cites the potential for diversifying local jobs outside the tourism sector.

Aventura Boats

The articulating conveyor is the key to efficient loading and unloading of the seaweed. Loading takes 10 minutes, unloading five.

Guessard says the CleanCat 42 would be part of a “superefficient” system that would also rely on sargassum barriers, but more ecologically friendly than those being used today with plastic components. Anyone who has walked the Atlantic side of a Caribbean island has witnessed the awful, multicolored litter. Aventura Boats would use barri­ers built from bamboo sourced from an agricultural co­op in the Dominican interior. “Our waters are already full of plastic waste. It’s terrible,” he says. “We should not try to solve one problem by potentially adding to another.”

With plastic­like characteristics but without the downside, bamboo is strong and resistant to seawater. Applying locally harvested bamboo to the prob­lem not only will reduce existing stocks but also encourage more production of bamboo, a plant with excellent carbon­sequestration qualities.

Once enough sargassum is trapped behind the bamboo barrier, the vessel would use a pair of conveyors to scoop up and store up to 706 cu ft (20m3) of weed. Loading takes just 10 minutes. At the beach, the same conveyors are reversed to unload the sargassum into a specially designed trailer, which takes five minutes. At this rate, Gues­sard said, an estimated 500m3 (17,657 cu ft) of “clean” sargassum can be removed and stored in a single day.

Eco-Tour Potential
The boat’s speed and suitability for less­than­perfect conditions allow a single Clean Cat with a crew of two to range over a wide area. “These boats can quickly move along the coast in patrols of two, three, or six boats, working together and cooperating with national forecasting agencies to respond to specific sargassum arrivals,” Guessard said. “And they can do this without exploding government and hotel budgets.”


Renderings of the CleanCat illustrate how the two conveyor belts, articulated in an upward orientation, can be run in reverse to offload sargassum into a trailer backed to the water’s edge.

Thinking like the eco­advocate and excursion company owner that he is, Guessard is pitching a secondary pur­pose for the CleanCat—the boat is designed to accommodate up to 12 pas­sengers during harvesting. “The hotels can organize eco­tours that educate their guests about the relationship between climate change and sargas­sum and communicate their green strategy to protect the environment, including regeneration of degraded reefs,” he said.

The first boat will be launched and motored to Punta Cana in April or May in time for testing. Guessard is hoping to fund further CleanCat production with help from a private­public part­nership in the Dominican Republic that has set aside $12 million for the Punta Cana sargassum problem. Gues­sard says he will also market the boat to his hotel customers throughout the Caribbean.


In the down position, the conveyors extend well below the catamaran hulls to pull accumulated floating seaweed up to the working deck.

Growing to Meet Demands
Aventura Boats, employing 40 skilled workers, has the ability to build 12 boats a year. At present, the factory is working to full capacity as resorts gear up for a post­COVID occupancy boom. Guessard said incorporating CleanCat orders into the schedule will force Avent ura to increase capacity—he wants to double it over the next couple of years—as the company simultane­ously readies its third­generation line of excursion boats.

Aventura Boats

The Aventura boat factory is nestled in hills that line the North Coast of the Dominican Republic. The experienced, skilled crew builds a range of hand-laid, open-molded fiber-reinforced-plastic catamarans to serve Caribbean resorts and tour operators.

At this point, it makes sense to look at what motivates boatbuilders: money obviously, but what if the builder in question is already working at capacity? “Do not say I am bored,” Guessard said. “But the thing is, in 2008 we were known only in the Dominican Repub lic and Turks and Caicos. We [had] not yet become a very ‘trustworthy’ company. Now, in 2022 we have big companies like Sandals [Resorts] for our customers, and it is very easy to sell boats….

“The challenge is to make the boats better but also to build them faster at the same time. This means improving tooling [new molds], a better process, and to invest in a CNC cutting machine.” Guessard intends to customize less, and following the example of production builders, will offer only a limited num­ber of optional layouts and features.

Role of the Resort
Jake Kheel is vice­president of the Grupo Puntacana Foundation, a non­profit wing of the beachfront vacation enterprise that dominates the Domini­can Republic’s tourism industry. The foundation’s mission is to promote sus­tainable development and protect the environment. Kheel laments having to become a reluctant expert on the sar­gassum phenomenon, ever since the noxious weed began rolling onto beaches 10 years ago. So far, the local resort has spent between $5 and $6 mil­lion on barriers and removal, he said.

Punta Cana conducted pilot tests for another company’s removal system, using a harvester barge; it was a failure. “We did some tests last year, and either the efficiency was low [they weren’t able to collect enough material], or the logistics [the time to unload] were too slow, or the cost was too high,” Kheel said. “They have told us they have ironed out all of these problems, but we have learned that in anything related to sargassum, seeing is believing, and the rest is probably hyperbole.”

Kheel said Punta Cana is continuing to look for better ways to harvest “clean, sand­free” seaweed that could be used for energy and agriculture. Though there are no plans to finance Aventura’s CleanCat project upfront, the Punta Cana Group has given Guessard’s crew run of the property to test the boat, including free marina dockage.

Because Punta Cana is such a huge player in the Caribbean, Kheel said other resort executives will travel there to witness CleanCat at work as they make purchasing decisions to deal with their own sargassum problems. For the purposes of marketing, Punta Cana sea­weed harvests would be the equivalent of buyers in the consumer market visit­ing the Miami International Boat Show, complete with demo rides.

Guessard’s maritime expertise brings a fresh skill set to bear, Kheel said, and there will be money in the budget if CleanCat proves to be a better solution. “The thing that we liked about his pro­posal is that he seems to have done his homework and sees what works and doesn’t work,” Kheel said.


Aventura Boats: A Dominican Phenomenon

[H]ow do you make a million dollars building boats/g oing into business in the D.R.? Answer: Start with two.

The punchline is the same whether the joke refers to prospective boatbuilders or foreigners wanting to go into any business in the Dominican Republic.

So, Lucas Guessard started with two strikes against him when he opened the Aventura Boats factory in 2005. Strike three? The absence of backing from a big investor. This Hispanic nation of 11 million people has a way of doing business that can be charitably described as tribal. As a hedge, savvy entrepreneurs often partner with a well­connected Dominican patrón, who acts as native guide and protector.

Aventura Boats

The first generation of Aventura dive boats were 30-footers (9.14m) made with molded fiberglass hulls and the remaining structure mostly plywood.

Instead, Guessard ventured to go it alone. And he beat the odds. Today, it is Guessard who is patrón to 40 employees, and his company builds more than $3 million worth of boats a year.

Guessard was born 54 years ago in Montpellier along France’s Mediterranean coast. As a child he sailed Opti­mist prams. At 12 he joined Sea Scouts, skippering a sail­ing skiff, which he and his crew repaired and main­tained—or “husbanded,” as the old Yankees used to say.

His epiphany came while watching a trimaran snatch victory during a yacht race on live TV. “I was fascinated to see this little yellow trimaran pass the big monohull at the finish line,” he said. Summer camp introduced him to the Hobie Cat 16, which he calls “the best little boat ever built.” From then on, like so many in the French sailing scene, Guessard became an unabashed multi­hull enthusiast.

He set out to earn a university degree in architecture but was drawn to an elec­tive course on boat design taught by Gerard Danson, founder of Outremer Catamarans. Guessard admired Danson’s somewhat contrarian design philosophy, whose essentials, according to one biog­rapher, included “long, slim hulls, low freeboard, low center of gravity, central weight distribution, and daggerboards.”

Sounds a lot like a big Hobie Cat, not the cumbersome multihulls now built for the charter trade.
He took a year off from college and hitchhiked under sail across the Atlantic, around the Caribbean, and back. Later, during a university internship in French Guiana, which gave him plenty of time to draw multihull designs, he learned that wood suitable for a quality strip­plank­and­epoxy boat was cheap in Brazil.

With financial support from his parents, he took yet another break from school, traveled to São Luís de Mara­nhão (a city founded by the French), and spent 16 months building a trimaran he would name Guara. During con­struction, Guessard lived in the family home of another boatbuilding mentor known as Portuguese Manuel, whom Guessard described as a self­taught genius.

Guessard and a younger brother (he has four) sailed the 32′ (9.75m) Guara around the Caribbean, eventually land­ing in Luperon on the North Coast of the Dominican Republic. They settled in and earned money taking guests from a nearby all­inclusive resort out sailing. The pro­ceeds from the excursion business subsidized his baby steps as a commercial builder, hiring a workforce of local teens and working harborside under a stand of trees.

His first big break came in 2001 when a dive company ordered a 30′ (9.14m) boat that could carry 14 divers and equipment. Guessard’s decision to build molds for fiber­glass construction turned out to be wise; he sold 33 of them over the next six years. The momentum from sales of this first­generation product allowed him to purchase 47 acres (19 hectares), where the Aventura factory was built in the village of La Culebra, about five miles (8 km) from the harbor. Now, every time a boat is launched, there is a parade from the hillside factory to the beach at La Isabela. Workers on the top deck must use forked tree branches to raise droopy electrical wires so the boat can pass, while others equipped with machetes chop through vegetation when necessary. Villagers, earning the equiv­alent of $200 a month, turn out to celebrate another $300,000 assemblage of shiny plastic being towed to the sea. To date, Aventura has sold 118 boats.

The factory sits on a small corner of Aventura land. The rest of the acreage is devoted to growing fruits and vege­tables, and beekeeping. Guessard hired an agronomist to get the farm started and establish a reforestation program. By the beginning of the 20th century, the local stands had been stripped of mahogany, most of it shipped north for he paneling and furnishings of mansions, not to mention yachts.

Aventura Boats

The first of the second-generation Arawak 42s is towed through the Dominican countryside in 2009 en route to its beach launching.

An Aventura co­op sells its homegrown produce and honey to its employees and local villagers at deeply dis­counted prices. Guessard is popular and widely admired in the region. Working at Aventura in an area of chronic underemployment is one of the best jobs around. The teens who helped him under the trees in 1999 are his factory leaders today.

None of which answers the initial question: How did Guessard succeed where so many have not? Magic may be the best answer. Gues­sard suggests otherwise: Maybe he was just a Dominican waiting to happen.

“I am unfortunately a messy, unorganized person, much better to adapt to a situation than to plan it, always waiting to the last moment to do things. And this is how most of the local people are. I am like a fish in the water here. Also, enjoying the spontaneity and no­stress attitude of the Dominicans, you make many friends, and those friends like to help you a lot. Most importantly, I was maybe born with a lucky star.”

– Peter Swanson

About the Author: Peter Swanson worked as a newspaper reporter and editor in New England for 20 years before running away to the Caribbean on a 30′ ketch. He came back and has written for boating magazines for the past 20. Along the way, he has varnished yachts, crewed on a schooner, delivered boats, and cap-tained excursion catamarans. He now publishes a popular e-mail newsletter about “boats, boating, builders, and waterways” called Loose Cannon.