There is no single worldwide commercial-diving certificate. IMCA, HSE, ADCI and ADAS are not four versions of the same thing — they are four different kinds of system. IMCA is an international contractors’ association that recognises national diving-certification schemes rather than issuing diver certificates itself. HSE is the UK regulator that publishes a list of approved diving qualifications for work in UK waters. ADCI is the American industry association that issues its own certification cards — the reference credential for commercial diving in the US, including the Gulf of Mexico. ADAS is Australia’s national diving-certification scheme, with a route for assessing foreign qualifications against it. Which one is relevant to you depends on where — and for whom — you plan to work.
What IMCA and HSE actually are
IMCA (the International Marine Contractors Association) is the body most offshore diving contractors work to, worldwide — including the North Sea and the Gulf. It does not certify individual divers. Instead, it maintains a list of national diving-certification schemes it recognises, and an employer working to IMCA guidelines expects your certificate to come from one of those recognised schemes.
HSE is different in kind: it is the UK’s statutory diving regulator, and it publishes a list of diving qualifications approved for professional diving work in UK waters. The Dutch B50/B50R qualification appears by name on that list. HSE reviews the list periodically, so treat that as current best information and check the live list before relying on it for a specific UK job.
ADCI and ADAS: two separate national systems
ADCI (the Association of Diving Contractors International) is the American industry association for commercial diving. It issues its own commercial-diver certification cards, based on the ANSI/ACDE training standard, and those cards are the reference credential for commercial diving in the United States, including the Gulf of Mexico. For divers trained outside that system, ADCI runs an international endorsement route through which a foreign background can be assessed. There is no confirmed mutual recognition between IMCA and ADCI — the two systems run independently — so do not assume an IMCA-recognised background is automatically accepted in an ADCI-run environment, or the reverse. In practice, US and Gulf-of-Mexico employers set out in each vacancy which certification they expect.
ADAS (the Australian Diver Accreditation Scheme) is Australia’s own national certification system. Its offshore qualifications — surface-supplied and closed-bell — are recognised by IMCA as a national scheme, the same kind of recognition the Dutch scheme holds. It includes an international-equivalence route through which a foreign qualification — including a Dutch, Hobéon-examined one — can be assessed against the ADAS standard. That is a case-by-case assessment route, not automatic acceptance of a foreign certificate.
Which certificate counts, and where
For work in UK waters, the HSE approved list is what matters. For offshore contractor work run to IMCA guidelines — across the North Sea, the Gulf and most other international offshore markets — what counts is that your certificate comes from a nationally recognised scheme on IMCA’s list. For work in the United States or the Gulf of Mexico, ADCI is the reference environment employers expect. For work in Australia, ADAS certification, or an assessed equivalence to it, is the standard.
These checks are not mutually exclusive: a diver can hold a nationally recognised qualification that satisfies IMCA-guided contractors while separately pursuing an ADAS equivalence assessment, or checking the current HSE list for a UK-specific job. Each is a distinct check, not one universal pass.
What this means for a diver trained in the Netherlands
The Dutch commercial-diving scheme, examined by Hobéon-SKO and registered with NDC-RI, is recognised by IMCA — which covers most offshore contractor work internationally. The B50/B50R qualification also appears by name on the UK HSE approved list, covering work in UK waters. For Australia, a Dutch qualification is not automatically an ADAS certificate, but it can go through the ADAS international-equivalence assessment.
For the US or the Gulf of Mexico, there is no confirmed automatic recognition of a Dutch, or otherwise IMCA-recognised, qualification within the ADCI system — check what a specific US employer or vacancy actually requires before assuming a certificate transfers.
Frequently asked
Is IMCA a diving certificate?
No. IMCA does not issue diver certificates. It recognises national diving-certification schemes, and offshore contractors working to IMCA guidelines expect your certificate to come from one of those recognised schemes.
Is HSE the same as IMCA?
No. HSE is the UK’s statutory diving regulator: it approves qualifications for professional diving work in UK waters. IMCA is an international industry association whose guidelines clients require contractually on offshore projects. They are different kinds of body — and for a UK offshore job you may need to satisfy both.
Is a Dutch diving qualification valid in the UK?
The Dutch B50/B50R qualification appears on the UK HSE list of approved diving qualifications, which covers work in UK waters. HSE reviews that list periodically, so check the current version before relying on it for a specific job.
Do I need ADAS to work in Australia?
ADAS is Australia’s national diving-certification scheme. A foreign qualification is not automatically equivalent — it can be assessed through ADAS’s international-equivalence route, which is a case-by-case process rather than automatic acceptance.
Which certificate do Gulf employers ask for?
It depends which Gulf. For offshore work in the Gulf region run to IMCA guidelines, a nationally recognised scheme is what counts. For the Gulf of Mexico, ADCI certification is the reference credential. Always check the specific vacancy.
Does ADCI recognise IMCA-approved qualifications, or the other way round?
There is no confirmed mutual recognition between IMCA and ADCI. The two systems run independently, and employers in each environment set out what they require on a job-by-job basis.