Offshore wind farms: vessels, cables and casualties, the maritime side

In August 2025, off the bay of Saint-Brieuc, a Dutch coaster carrying tower sections drifted a few hundred metres off its track and crossed the laying zone of an inter-array cable. The anchor touched nothing. The cable-laying vessel, however, stopped work for thirty hours to survey the seabed, and invoiced the standby time to the installation contractor, who passed it on to the developer, who refused to pay. Nobody suffered any physical damage. The dispute is worth €900,000.

The firm acts for wind farm developers and operators, construction and installation contractors, owners of service vessels, manufacturers and carriers of components, fishermen and other sea users, and insurers. It approaches offshore wind from the sea rather than from the energy side: occupation titles, vessels, construction and transport, cables, liability, insurance, disputes. This page extends the firm’s maritime law pillar page.

This page is the maritime side of our offshore energy practice. The overall framework, from planning to award, from consents to grid connection, from financing to decommissioning, is set out on our offshore energy law page; here you will find what happens at sea and on the water: service vessels, transport of components, cables, contacts and damage, insurance and disputes.

The legal space: territorial sea, EEZ and continental shelf

A wind farm does not sit on ordinary territory. In the territorial sea, the State exercises sovereignty and the seabed forms part of the maritime public domain. Beyond it, Article 56 of the Montego Bay Convention of 10 December 1982 gives the coastal State sovereign rights to exploit the resources of the exclusive economic zone, including energy from the wind, and jurisdiction over artificial islands, installations and structures. Article 60 provides that the coastal State has the exclusive right to authorise, operate and regulate them, and its paragraph 5 sets the breadth of safety zones: no more than 500 metres around each point of the outer edge, unless international standards provide otherwise. Article 80 applies the same regime to the continental shelf.

In French law, Ordinance No. 2016-1687 of 8 December 2016 on maritime areas brought these scattered rules together: baselines, territorial sea, contiguous zone, exclusive economic zone, continental shelf, authorisation of installations, cables, safety and site restoration. It is the starting point for any analysis of a farm’s footprint.

Law No. 2023-175 of 10 March 2023 on accelerating the production of renewable energy shifted the centre of gravity of these projects upstream. The logic is no longer that of an isolated project put to public debate, but that of planning: a national public debate held from November 2023 to April 2024 led to maps of priority zones, carried over into the strategic documents for each seaboard. The choice of zones is therefore argued before the tender, not after. Sea users who wait for the competitive procedure under Articles L. 311-10 et seq. of the Energy Code to raise their objections almost always come too late. This is the first trap in the field, and it is fatal. Law No. 2018-727 of 10 August 2018 also introduced, in its Article 58, the environmental authorisation with variable characteristics, the so-called “envelope permit”, which allows the project to be described by ranges of values and the turbine to be chosen later.

Occupying the maritime public domain and the EEZ

The nature of the occupation title changes with distance from the coast. In the territorial sea, outside port limits, the footprint of the foundations, cables and substation falls under the concession to use the maritime public domain provided for by the General Code of Public Property, at Articles L. 2124-1 to L. 2124-3, processed under Decree No. 2004-308 of 29 March 2004. Beyond that, in the exclusive economic zone and on the continental shelf, the installation falls under a separate authorisation regime, derived from Decree No. 2013-611 of 10 July 2013 and later recast by the 2016 Ordinance.

Three clauses deserve more attention than they usually get. First, the term, which must cover the industrial life of the farm and the decommissioning period, or the operator will end up negotiating an extension from a weak position. Next, the fee, whose basis and indexation formula are negotiated during the application process and almost never afterwards. Finally, the financial guarantees for decommissioning, which tie up considerable sums and whose amount, form and release conditions shape the financing plan.

Then there is coexistence. The occupation title does not create an absolute private right over the water column: navigation and fishing continue, subject to safety zones and the orders of the maritime prefect. Fishermen are compensated in particular through the annual tax on installations generating electricity from offshore wind, provided for in Articles 1519 B and 1519 C of the General Tax Code, part of whose proceeds goes to the fisheries committees. The tax does not extinguish individual claims. It only makes them harder to quantify, since the defendant will argue that the fisherman has already been compensated collectively.

Construction, manufacturing and transport of components

A farm is built in packages: foundations, turbines, offshore substation, cables. Some developers prefer a single EPCI contract, others split the packages to get the best price on each. The second option saves money at signing and costs it during installation, because it transfers the management of interfaces to the employer. Who is liable for delay when the installation vessel is waiting for foundations that have not been delivered? The answer is not in the installation contract but in how the two contracts fit together, and that is where the drafting turns out to be silent.

Transporting components is heavy-lift carriage by sea and it follows ordinary maritime law. Depending on whether the voyage is performed under a bill of lading or a voyage charterparty, the liability regime, time limits and caps differ, as explained on our carrier liability page. Securing a 110-metre blade is not a technical detail: it is where liability is divided between shipper, carrier and lashing contractor, and the first thing the surveyor will look at. Force majeure clauses and weather windows call for the same rigour, since a poorly defined wave-height criterion turns every week of bad weather into an argument about liquidated damages.

Floating wind raises a question the law has not settled. The Mediterranean pilot farms rest on floaters built in a shipyard, towed, then moored. Is such a floater a ship, capable of registration, mortgage and arrest, or an offshore installation? No general answer is available in French law today, and in practice the characterisation adopted by the parties in their contracts and policies is what will decide the first dispute.

Service vessels

The farm lives through its vessels: crew transfer vessels, service operation and accommodation vessels, self-propelled jack-ups for lifting, cable-laying vessels for installation and repair. These units are chartered on a time basis using specialised forms. BIMCO publishes SUPPLYTIME 2017 for offshore support vessels and WINDTIME, in its 2013 edition, designed for the time chartering of vessels carrying personnel and equipment to offshore wind installations. What they have in common is the knock-for-knock clause: each party bears its own personal injury and property damage, whoever is at fault. The clause is effective and blunt. Our charterparty disputes page explains how these contracts work.

Then comes the question of flag. Council Regulation (EEC) No. 3577/92 of 7 December 1992, in force since 1 January 1993, applies the freedom to provide services to maritime cabotage and allocates jurisdiction over manning rules between the flag State and the host State. In France, Law No. 2005-412 of 3 May 2005 created the French International Register, and Articles L. 5561-1 et seq. of the Transport Code subject foreign vessels operating in French waters to the host State’s social conditions. The authorities inspect, and they detain.

The status of technicians on board remains the most poorly handled point in these files. A maintenance technician who spends twenty days on an accommodation vessel is not necessarily a seafarer, since Article L. 5511-1 of the Transport Code distinguishes seafarers from other personnel employed on board. That characterisation determines the social security regime, the contract, the competent court and the insurance cover. Our seafarers page deals with this boundary.

Subsea cables

The cable is the most vulnerable part of the farm and the one that has been protected the longest. The Paris Convention of 14 March 1884 for the Protection of Submarine Telegraph Cables, still in force, penalises breaking a cable wilfully or through culpable negligence. The Montego Bay Convention takes up this regime in Articles 113 to 115: States must punish the breaking or injury of a submarine cable beneath the high seas done wilfully or through culpable negligence, except where the ship acted to save life or its own safety; the owner of a cable who damages another cable while laying it bears the cost of repair; and, under Article 115, the cable owner must compensate a shipowner who proves that it sacrificed an anchor, a net or other fishing gear to avoid damaging the line. That last rule is little known among skippers. It works in their favour.

Two networks must be distinguished. The inter-array cables, owned by the operator, link the turbines to the substation. The export cable, which runs to shore, is built and financed in France by the public transmission system operator, under Articles L. 342-3 et seq. of the Energy Code. The ownership boundary between the two determines who sues the vessel at fault and who bears the loss of production during repairs.

In practice, damage comes from anchors and trawls. A claim against the owner of the vessel at fault runs into two obstacles: proving the vessel’s passage, which is reconstructed from positioning data and a seabed survey, and the limitation of liability under the London Convention of 19 November 1976, which the shipowner almost always invokes. The cable insurance, often written with business interruption cover, then becomes the real payer, and the subrogated recovery action the real dispute.

Liability

A vessel strikes a turbine or the substation. The reflex is to apply the collision rules. It is a mistake, and it costs both on the burden of proof and on time limits: a fixed installation is not a ship, so the allision falls under ordinary liability, on the basis of Article 1240 of the Civil Code, and not under collision law, which comes back into play as soon as a service vessel is involved in the collision. Our ship collision page sets out that second regime.

Damage to fishermen and other sea users forms the largest body of claims and the hardest to value: loss of fishing grounds, longer routes, nets snagged on poorly charted rock protection. Pollution follows two distinct regimes. Bunker oil from a service vessel falls under the Bunkers Convention of 23 March 2001 and the framework described on our marine pollution page, while fluids from a nacelle or transformer fall under the Environmental Code and the rules governing installations. The concession holder is liable to third parties, including at the end of the farm’s life, when decommissioning leaves foundation bases or sections of cable behind.

One point remains open. Article 15(5) of the 1976 London Convention excludes from limitation floating platforms constructed for the exploration or exploitation of the natural resources of the seabed. A wind floater exploits the wind, not the seabed. The wording of the text therefore suggests that it is not excluded. No reported decision has ruled on it. We draft the clause saying so.

Insurance

Building a farm is insured under a construction and erection policy, often supplemented by delay in start-up cover for the margin lost during the months of missing production. On top of this come cargo insurance for transporting components, hull policies and P&I cover for the service vessels, and operational liability insurance once the farm is in service. Our marine insurance page describes these mechanisms.

One question keeps coming back and has not been settled: does the builders’ ten-year liability (garantie décennale) apply to an offshore wind turbine? The Civil Code refers to building and civil engineering works, and to our knowledge the courts have never ruled on a foundation installed in the exclusive economic zone. We know of no reported decision. Negotiating a policy on the assumption that the ten-year guarantee applies means buying a risk that nobody has priced.

The real work lies in how the covers fit together. Damage to a cable during laying may fall under the construction policy, the cable-layer’s hull policy, the installer’s liability cover or the knock-for-knock clause of the charterparty, depending on the date of acceptance and the wording of the waivers of subrogation. Those waivers are the most powerful and most misused lever in the file: granted too broadly, they deprive the insurer of any recovery and come back to bite the insured at the next renewal.

Disputes

Challenges to consents and concessions have been centralised. After a first stage in which Decree No. 2016-9 of 8 January 2016 gave jurisdiction to the Nantes Administrative Court of Appeal, Article R. 311-1-1 of the Code of Administrative Justice, as amended by Decree No. 2023-1419 of 29 December 2023 and applicable since 1 January 2024, gives the Conseil d’État jurisdiction at first and last instance over challenges to decisions concerning offshore renewable energy installations and their associated works, from the operating licence to the environmental authorisation and occupation titles. There is now a substantial body of case law. In decisions No. 416862 and No. 418846 of 24 July 2019, concerning the farm off Saint-Brieuc, the Conseil d’État held that the selection procedure had been irregular because one criterion had not been disclosed to bidders, without however annulling the farm’s authorisation, and awarded damages to the unsuccessful bidder. In its decision of 23 November 2022, No. 440628, given by the combined 6th and 5th chambers concerning the Yeu and Noirmoutier farm, it upheld the practice of an improved offer after selection and before signature.

Contractual disputes take a different route. Construction and installation contracts refer to arbitration under the International Chamber of Commerce, while service vessel charterparties most often designate the London Maritime Arbitrators Association, and the Paris Maritime Arbitration Chamber remains the natural forum for chartering disputes governed by French law. A single casualty can thus open three parallel proceedings before three different forums. Coordinating them is the first strategic decision, before any argument on the merits.

Then there are enforcement proceedings, often the quickest. An unpaid owner of a crew transfer vessel can use the conservatory arrest described on our ship arrest page, and a court-ordered survey at sea, obtained in summary proceedings, requires a precisely drafted brief: dives, surveys, positioning data, examination of recorders.

How the firm works

The firm advises developers and operators on occupation titles, decommissioning guarantees and the defence of consents. It advises construction and installation contractors on EPCI contracts, interfaces between packages and delay claims. It advises owners of service vessels on SUPPLYTIME and WINDTIME charterparties, manning conditions, detentions and unpaid hire. It assists fishermen and other sea users with their challenges and compensation claims, and insurers with the conduct of surveys and subrogated recovery actions.

Our work starts with reading the contracts and policies, continues with securing the evidence, and leads, depending on the case, to a settlement, an arbitration or court proceedings.

Based in Paris, the firm acts in every French port, in mainland France and overseas, before the commercial courts and civil courts of the coast, and before the Paris Maritime Arbitration Chamber, and works in English with P&I clubs, insurers and foreign counsel.

The firm’s analyses and guides

Charterparties for service vessels are covered in detail on our charterparty disputes page, and the procedural routes available when a dispute arises on our maritime litigation page. For drafting and negotiating contractual documents, the maritime contracts guide goes through the points of friction clause by clause. The shipping decarbonisation guide places offshore wind within the regulatory framework for emissions, and the autonomous ships guide deals with the uncrewed surveillance and inspection units now used on wind farms.

Frequently asked questions

Can you fish inside an offshore wind farm?

The occupation title does not make the area private. Fishing and navigation remain possible, except in safety zones and subject to the orders of the maritime prefect. Article 60(5) of the Montego Bay Convention caps these safety zones at 500 metres around each point of the outer edge of the installation, unless generally accepted international standards provide otherwise. In practice, the restrictions vary from one farm to another and are found in the applicable order, not in the concession.

Who pays when a trawl tears out a wind farm cable?

The cable owner sues the owner of the vessel at fault, and must prove the vessel’s passage and fault. The shipowner usually invokes the limitation of liability under the London Convention of 19 November 1976. Conversely, Article 115 of the Montego Bay Convention provides that a shipowner who proves that it sacrificed an anchor, a net or other fishing gear to avoid damaging the cable is compensated by the cable owner.

Is a wind turbine floater a ship?

The question has not been settled in French law. A floater is built in a shipyard, towed, then permanently moored; once installed it has neither propulsion nor crew. The characterisation governs registration, mortgage, conservatory arrest and hull insurance. No reported decision has ruled on it to date. The parties have every interest in fixing the characterisation themselves in their contracts and policies, rather than leaving a judge to discover it after the casualty.

Which court hears a challenge to an offshore wind farm’s consent?

The Conseil d’État rules at first and last instance on challenges to decisions concerning offshore renewable energy installations and their associated works, under Article R. 311-1-1 of the Code of Administrative Justice, applicable since 1 January 2024; the Nantes Administrative Court of Appeal, which had jurisdiction under Decree No. 2016-9 of 8 January 2016, no longer hears challenges lodged since that date. This single-tier route shortens the timetable, but it concentrates the whole factual debate before one court, which means producing all the evidence with the application.

Is a technician who sleeps on board a farm vessel a seafarer?

Not necessarily. Article L. 5511-1 of the Transport Code distinguishes seafarers, who carry on a professional activity on board, from other personnel employed or working on board. A wind turbine maintenance technician often falls into the second category. The distinction determines the applicable contract, the social security regime, the competent court in a dispute and the insurance cover in the event of an accident during a transfer onto the turbine ladder.

What does a knock-for-knock clause mean in a service vessel charter?

Each party bears the damage suffered by its own property and its own personnel, with no recourse against the other, even where the other is at fault. BIMCO’s offshore forms, including SUPPLYTIME 2017 and WINDTIME in its 2013 edition, are built on this allocation. The advantage is predictable insurance: each party insures what it knows. The risk is surprise, when a charterer discovers after the accident that it bears the loss of equipment worth several million carried on the vessel.

Who builds and pays for an offshore wind farm’s grid connection?

In France, the export cable and the onshore delivery substation are built and financed by the public transmission system operator, under Articles L. 342-3 et seq. of the Energy Code. The inter-array cables and the offshore substation remain the operator’s responsibility. The ownership boundary determines who sues the vessel at fault in the event of damage and who bears the loss of production during repairs. It is set out in the connection agreement.

Does the ten-year builders’ guarantee cover an offshore wind turbine?

The question is unresolved. The ten-year guarantee under the Civil Code covers building and civil engineering works, and to our knowledge no reported decision has applied it to a wind turbine foundation installed at sea, still less beyond the territorial sea. Insurance programmes therefore deal with the issue contractually, through performance and maintenance guarantees negotiated package by package. Relying on the ten-year guarantee without having stipulated it is a gamble.

Matters in this field are handled by Hervé Guyader, avocat at the Paris Bar and doctor of law.