How to choose a kelp farm boat: match vessel class to farm stage, run the real total-cost math, weigh new vs used vs leased, and sea-trial before you sign.
The boat will likely be your farm's second-largest purchase after the mooring grid, and the only one that can sink. Most first-time growers choose it the wrong way around: they fall for a hull, then discover the work. This guide turns the process over. We start from the farm's task list and stage, match a vessel class to it, price the true cost of a season's boating, and only then look at listings. Think of it as the purchase-order version of our operator's-eye tour of workboats and deck tools — that article covers rigging the deck; this one covers deciding what deck to buy.
Spend an evening with a spreadsheet, not a boat broker. List every job the vessel must do in its busiest fortnight, with the numbers that size each job:
Be honest here. Growers routinely buy for the farm they hope to have in year four; boats are cheaper to upgrade than businesses are to repair.
| Farm stage | Typical footprint | Vessel profile that fits |
|---|---|---|
| Trial or pilot lease | A few lines, a shared site | No owned vessel. Charter by the day, or ride-share with the operator whose gear you are trialling beside. |
| First production farm | Roughly half a hectare to two | A 5–7 m open skiff or small cabin skiff, trailerable, single outboard, working rail aft. This is the buyer's sweet spot. |
| Established coastal farm | Two to ten hectares | 7–10 m wheelhouse workboat, cat or landing-craft layout, hydraulic hauler, twin engines or single diesel — chosen for the site's exposure. |
| Offshore or multi-site operator | Ten hectares plus | Purpose-outfitted vessel with crane capacity, plus contracted heavy-lift days for mooring work; or a shared asset with neighbouring farms. |
Two patterns hide in that table. First, an owned boat only earns its berth once the farm calls on it weekly; below that, contracting lifts and transits beats ownership on cost and sleep. Second, each step up the table is roughly a doubling of operating budget, not a step — which is why the farm economics and the vessel decision should be signed the same week, not in different years.
Four doors, and most farms should walk through two of them across a season rather than picking one.
The common failure mode is buying for the two hardest days of the year and paying for them the other three hundred and sixty-three.
Purchase price is the cover charge. Build the full annual figure before you commit:
| Cost line | First-year weighting | What growers forget |
|---|---|---|
| Purchase or lease | Highest | Fit-out is rarely included: hauler, rail gear, electronics, safety kit can add a meaningful fraction of hull price. |
| Insurance and survey | Annual | Most insurers want a marine survey on used hulls; budget it as a buying tool — a survey is the best money you will spend. |
| Berth, mooring or trailer | Annual | Trailer boats need trailer maintenance and a compliant tow vehicle, not just a driveway. |
| Fuel and oil | Per engine hour | Offshore sites multiply this line; plan from the chart distance of your worst week. |
| Maintenance and antifoul | Annual | Salt water bills on a schedule regardless of use. Haul-out weeks are also lost working weeks. |
| Depreciation | Silent | Workboats retain value when maintained and shed it fast when not. This line decides whether a cheaper boat was actually cheaper. |
| Training and licensing | One-off plus renewal | Small-commercial-vessel tickets, radio certificates, first aid — the flag state's code for your size of vessel applies whether your farm is a business or a dream. |
Run the table for each candidate vessel, not just the favourite. The right boat is the one whose annual number the crop can carry, which is a question your farm budget answers, not the broker.
New buys warranty, known history, exact fit-out and financing options — and pays for them. First farms rarely need new.
Used is where nearly every working kelp fleet comes from, and it rewards discipline:
A test spin around the marina proves the engine starts. It proves nothing else. Trial under work:
Score candidates against the Step 1 work profile, out of ten per job, weighted by frequency. It feels clerkly until the first season belongs to the boat that scored second.
Every growing farm meets the moment when one vessel is the single point of failure for the entire crop — usually in week two of harvest. Plan the redundancy path at purchase time: a trailerable first boat makes a backup skiff cheap to add later; a contracted-lift relationship keeps a spare deck one phone call away; a neighbouring grower with a reciprocal breakdown agreement is worth more than either. Resilience thinking here mirrors redundancy thinking everywhere else on the farm — the same logic behind storm-preparedness and choosing the site itself.
And if your background is artisanal fishing rather than aquaculture, note that the vessel decision often travels with a livelihood transition — the pathways in our fisheries solution are built around exactly this kind of asset staging.
For a pilot lease, none — charter. For a first production site of up to about two hectares, a trailerable open skiff in the five-to-seven-metre class with a working rail aft covers nearly every task, provided the site is within sensible run of the ramp. The step up to a larger wheelhouse vessel should be justified by weekly working hours, not ambition.
Used, for most first farms, with a professional marine survey as a non-negotiable part of the price. New makes sense once the operation is proven and the fit-out is well understood — the warranty and known history then buy real downtime risk reduction.
It depends on vessel size, distance from shore, and whether your operation counts as commercial in your jurisdiction — which it usually does. Your flag state's small-commercial-vessel code will specify operator certification, radio qualifications, safety equipment and possibly periodic inspection. Check the authority before you buy; the code can shape the boat as much as the budget does.
Sometimes, briefly — but check three things first: insurance (recreational policies often exclude commercial use), payload at the working rail under harvest load, and deck layout (grow-line and seed-spool work fouls on furniture fast). Many growers start this way and discover within a season why workboats are shaped like sheds.
Buying for the two hardest days of the year. The crane-scale jobs — setting anchors, recovering moorings — come twice a season, and chartering them is nearly always cheaper than owning the capacity. Buy for the weekly work; rent the exception.
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