Commercial diving is a fast paced and time critical industry, and it is also one of the most heavily regulated. When a project runs offshore on a wind farm, inland on a civil engineering contract, or inshore on a harbour inspection, the people planning that work carry clear legal duties. Get the framework wrong and the consequences are not only operational; they are legal, and they put lives at risk. Get it right and the same framework becomes a reliable structure for planning safe, defensible operations.
This guide explains the UK regulatory framework for commercial diving in plain terms: the single set of regulations that governs all diving at work, the five Approved Codes of Practice that sit beneath them, the roles the law defines, and the qualifications and medicals a working diver must hold. It is written for dive supervisors, contractors, vessel and project managers, and procurement teams who need to understand what the law requires and who is accountable for what.
In summary: All commercial diving in Great Britain is governed by the Diving at Work Regulations 1997. These are supported by five Approved Codes of Practice (ACOPs), one for each sector of the industry, which the Health and Safety Executive (HSE) revised and brought into force on 8 December 2014. The Regulations set out a clear chain of responsibility — diving contractor, supervisor and diver — and require every project to be planned, risk-assessed and supervised. Divers must hold an HSE-approved qualification and a valid certificate of medical fitness to dive.
The Diving at Work Regulations 1997: the foundation
The main set of regulations that apply to diving are the Diving at Work Regulations 1997 (often shortened to DWR). They were made under the Health and Safety at Work etc. Act 1974 and came into force on 1 April 1998, replacing the earlier Diving Operations at Work Regulations 1981. They cover all dives where one or more divers are at work, whether employed or self-employed.
The Regulations define diving in a specific, technical way. For legal purposes a person “dives” if they enter water or another liquid, or a chamber subject to a pressure greater than 100 millibars above atmospheric pressure, and in order to survive in that environment they breathe air or other gas at a pressure greater than atmospheric. That definition is what brings an activity within scope of the Regulations.
A few activities sit outside the Regulations. They do not apply to the emergency medical treatment of patients in a hospital or in transit to one (where that place is not under the control of the diving contractor), to members of the armed forces engaged in warfare or training for warfare, or to work in compressed air used to keep ground water out of civil engineering works. Nearly all commercial diving falls squarely within scope.
A key point for operators working outside UK territorial waters: the Regulations extend to diving projects on the UK Continental Shelf and other premises and activities to which the Health and Safety at Work Act applies outside Great Britain, so offshore energy and oil and gas work is covered.
Goal-setting law, not a rulebook of numbers
An important thing to understand about the DWR is that they are “goal-setting” regulations. They do not, in the main, prescribe in fine detail exactly how a dive must be carried out. Instead they place duties on the people responsible and require the work to be planned and managed so that health and safety is protected, so far as is reasonably practicable.
The practical detail — how to actually meet those duties in a given sector — lives in the Approved Codes of Practice. This two-layer structure is why you cannot answer a real-world compliance question from the Regulations alone; you read the Regulations for the duties and the relevant ACOP for the accepted way of discharging them.
The five Approved Codes of Practice
The HSE has issued five Approved Codes of Practice under the Diving at Work Regulations 1997, one for each sector of the diving industry. All five were revised following industry consultation and came into force on 8 December 2014. An ACOP has a special legal status: following it is not compulsory, but if you are prosecuted for a breach of the law and did not follow the relevant ACOP, you will need to show you complied in some other equally effective way.
| ACOP | Sector | Typical work |
|---|---|---|
| L103 | Commercial diving projects offshore | Diving in support of offshore oil and gas and offshore energy — including on the UK Continental Shelf, wind farms and pipeline works. Covers closed bell and saturation diving. |
| L104 | Commercial diving projects inland/inshore | Civil engineering, marine construction, inspection, harbour and inshore projects, fish farming and similar work in UK inshore waters. |
| L105 | Recreational diving projects | Instruction and guiding of recreational divers where at least one person taking part (for example an instructor) is at work. |
| L106 | Media diving projects | Diving for television, film, journalism and performance — including presenters, camera and sound crew and stunt performers. |
| L107 | Scientific and archaeological diving projects | Diving in support of scientific research, education and archaeological investigation. |
For most iSubC customers the two most relevant codes are L103 (offshore) and L104 (inland/inshore). Both set out the accepted approach to planning, supervision, equipment and emergency arrangements for their sector.
Who is responsible? The chain of duty-holders
One of the clearest features of the Regulations is that they define specific roles and attach specific duties to each. Everyone involved in a diving project has responsibilities — from the client commissioning the work through to the diver in the water — but three roles carry defined legal duties.
The diving contractor
Every diving project must have one diving contractor, and one only. The diving contractor is normally the employer of the divers, or a self-employed diver working alone. Where more than one party could qualify, they must appoint one of themselves in writing, before the project starts, to act as the diving contractor.
The diving contractor carries the top-level duty to ensure, so far as is reasonably practicable, that the project is planned, managed and conducted to protect the health and safety of everyone taking part. In practice this includes:
- Ensuring a diving project plan is prepared before work starts, and kept updated as the project continues.
- Appointing a supervisor for each diving operation in writing, and giving them the relevant part of the plan.
- Ensuring there are enough competent people, and suitable and sufficient plant, to carry out the work and to deal with a reasonably foreseeable emergency, including first aid.
- Ensuring that plant is maintained in a safe working condition.
- Ensuring a diving operation record is kept, and retaining it for at least two years after the last entry.
The supervisor
Each diving operation is placed under the direct personal control of a supervisor. Only one supervisor may be appointed to supervise a diving operation at any one time, and they must be competent and, where appropriate, suitably qualified for the operation concerned. The supervisor must ensure the operation is carried out without risk to health and safety so far as is reasonably practicable, in line with statutory requirements and the diving project plan; make sure everyone taking part knows the relevant parts of the plan; and complete the diving operation record as the work proceeds.
The supervisor also has the power to give reasonable directions to anyone taking part in, or who could affect the safety of, the operation. As a general rule the supervisor must not dive during the operation they are supervising, other than in narrow exceptions set out in the Regulations (for example certain recreational or training situations using self-contained breathing apparatus).
The diver
Divers carry duties too. No diver may dive in a diving project unless they:
- Hold an approved qualification valid for the activity they may reasonably expect to carry out; and
- Hold a valid certificate of medical fitness to dive.
Every diver must also keep a daily record of their diving and retain it for at least two years after the last entry. And no one may dive if they are not competent for the work, or if they know of anything — including any illness or medical condition — that makes them unfit to dive. Divers must follow the supervisor’s directions and the instructions in the project plan.
Notifying HSE: the diving contractor’s registration duty
Before acting as a diving contractor, a business must supply certain particulars in writing to the HSE — essentially its name, address and telephone number, its legal status, a contact in case of need, and the name and signature of the person supplying the details. If any of those particulars change, the contractor must tell HSE straight away. This is a one-off company notification, not a per-project permit, and it does not apply where everyone diving in the project is doing so purely for recreational purposes.
Qualifications: what a working diver must hold
To work as a diver in Great Britain you must hold a qualification approved by HSE that is relevant to, and sufficient for, the work. HSE recognises four assessment standards of commercial diving competence:
- HSE SCUBA — where the breathing gas is carried in cylinders worn by the diver (Self-Contained Underwater Breathing Apparatus).
- HSE Surface Supplied — where the diver receives breathing gas via an umbilical from the surface.
- HSE Surface Supplied (Top-Up) — an additional assessment required to dive offshore on surface supplied equipment.
- HSE Closed Bell — for closed bell and saturation diving using mixed gas, where divers can transfer to the worksite in a bell and live in a compression chamber complex for extended periods.
Competence for these standards is assessed by diver competence assessment organisations recognised by HSE. If a candidate does not reach the required standard, they can appeal within 28 days using the assessment organisation’s appeals procedure.
Depth limits
HSE diving qualifications carry a depth limit of 50 metres, with the exception of Closed Bell, which has no depth limit. That 50-metre limit applies to surface supplied diving in the Offshore, Inland/Inshore, Shellfish and Police classes. Closed bell divers use mixed gas precisely because it allows them to work safely beyond 50 metres.
A recent change worth noting
From 1 January 2025, HSE only recognises Spanish Surface Supplied diving qualifications where the diver also holds an HSE Top-Up qualification. Contractors checking the competence of divers who qualified in Spain should confirm the diver’s status against the current HSE List of Approved Diving Qualifications. It is a useful reminder that the approved list is a live document, and the right practice is always to verify against the current version rather than rely on what was accepted previously.
Medical fitness to dive
A valid certificate of medical fitness to dive is a legal requirement for every working diver. The certificate is issued by an Approved Medical Examiner of Divers (AMED) following a medical examination, and it can state a validity period of no more than 12 months. It may carry limitations or conditions, and it can be revoked on medical grounds at any time.
The process usually begins with the diver completing a medical questionnaire (the MA1 form) with their GP before the examination. If a certificate is refused, limited, made conditional or revoked, the diver can appeal to HSE within 28 days, and HSE will review the decision.
The wider legal picture
The Diving at Work Regulations do not sit in isolation. Diving projects also engage the general duties of the Health and Safety at Work etc. Act 1974 and other regulations — for example the reporting of certain injuries and dangerous occurrences, pressure systems requirements for chambers and cylinders, and confined space requirements where relevant. Breathing gas quality is a practical example: a competent person should test the quality of the air supplied for breathing apparatus at least once every three months, and more frequently if contamination is foreseeable within that period.
For UK operators the governing framework is HSE-led. Internationally, and for many offshore contracts, industry standards from bodies such as the International Marine Contractors Association (IMCA) and guidance from the Diving Medical Advisory Committee (DMAC) sit alongside the legal requirements. Where a contract calls for equipment built and certified to those standards, the specification needs to be right from the outset.
What this means for your equipment
Regulatory duties translate directly into equipment decisions. A diving project plan that is sound on paper still depends on plant that is suitable, sufficient and properly maintained — that is a direct duty on the diving contractor. Breathing gas systems, chambers, panels, communications and launch and recovery equipment all need to match the class of diving and the standards the contract demands.
At iSubC we supply commercial diving equipment worldwide, new, used and for hire, and we build bespoke systems to IMCA standards, including “witness” and “built to class” systems. We understand the industry is fast paced and time critical, so we focus on honest, realistic delivery timeframes and clear communication, and we ship door to door by sea or air freight. Whether you need surface supplied panels, hyperbaric medical equipment, launch and recovery systems or a full containerised dive system, we can help you specify equipment that fits both the job and the standards that govern it.
