On a subsea project the client can't see what's been done, so what they're buying is the record: time-and-depth-referenced video, measurements, photographs, dive logs and an as-built that shows how the installation actually ended up. A job done well but documented badly counts as unproven, and it often has to be redone.
There's a line that gets repeated in the project offices of almost every subsea contractor: if it isn't documented, it didn't happen. It sounds like administrative exaggeration until you see the situation from the other side. The client is paying for work that happens tens of metres underwater, somewhere they can't go themselves, on a structure they may not inspect again for five years. The only thing they get is the record.
That's why documentation isn't the paperwork you do at the end. It's part of the deliverable, carrying the same weight as the welding or the part replacement, and it often eats up more hours than people expect when they're starting out in the trade.
What documentation a subsea project generates
The dive log
It's the base document, and the supervisor signs it. It records who went down, at what time, to what depth, on what mix, how long they were on the bottom, what decompression they did, what task they carried out and any incidents. Beyond its technical function it has a legal one too: it's the record of a person's hyperbaric exposure, and if a medical problem shows up later, it's the first thing that gets reviewed.
The supervisor's log also feeds into the logbook personal of each diver, though they're separate documents with separate owners.
The video
Almost all modern inspection work is recorded. The helmet camera, the hand-held camera or the ROV's camera produce hours of footage that's only worth anything if it's referenced: an on-screen overlay with date, time, depth and, where the system allows, position. Without that reference, an underwater video is just a blurry shot of metal that proves nothing.
The diver's narration is part of the record. A good inspection diver describes out loud what they see as they see it, using consistent vocabulary: where they are, what element they're looking at, what anomaly they've spotted, what dimension they estimate. That audio track is what later lets someone find the exact minute within six hours of footage.
Still photography and measurements
Photos are for the written report, where a frame grabbed from video usually looks poor. They're taken with a visible scale in shot: a ruler, a graduated marker or something of known size in the frame. Without a scale, a two-millimetre crack and a two-centimetre one look much the same.
Measurements cover everything from wall thickness and pitting depth to position coordinates. On pipeline tie-in work, measurement becomes a discipline of its own with its own procedure, which is what we cover in the article on underwater metrology.
The anomaly log
When something is found that shouldn't be there — a crack, a wasted anode, a loose fitting, impact damage — it goes into an anomaly log with a unique identifier, location, description, dimension, severity and supporting evidence. That log is what later feeds the client's maintenance plan, and what decides whether someone has to come back next month or in three years' time.
The severity classification isn't the diver's to invent: it comes from the client's procedure. The team's job is to describe accurately, without over-rating or under-rating. Overstating an anomaly leads to expensive, unnecessary interventions; playing it down is a safety problem.
What an as-built is, and why it matters so much
The design says how the installation should end up. The as-built says how it actually ended up. There's always a difference between the two documents, because underwater nothing fits exactly as drawn: there are tolerances, ground conditions that weren't what was expected, parts installed slightly off, and fixes decided on site.
A complete as-built includes the updated drawings with the actual dimensions, the list of materials actually installed with their traceability, the certificates for the procedures applied, the deviations from the design with their justification, and visual evidence of the final condition.
Its usefulness shows up years later. When someone has to work on that structure again, the as-built is what tells them what they're going to find. If it's wrong, the next team goes down with a plan that doesn't match reality, and that costs vessel time, which is the most expensive unit of money in the industry.
How to get the documentation right
Document as you go, not afterwards
The classic mistake is leaving the paperwork until the end of the shift, by which point nobody remembers whether the pit was on the third brace or the fourth. Teams that work well record it while it's happening: the supervisor writes it down while talking to the diver, and the shift report is closed before handover.
Vocabulario consistente
If one shift calls a part a "connection flange" and the next calls it a "collar", the final report is unusable. Serious projects fix a naming convention and an element ID system from day one, and everyone uses it, even when it feels clumsy.
Language
On international projects the documentation is written in English, regardless of the crew's nationality. Writing a clear technical report in English is a skill that gets paid for, and it's one of the reasons we push technical English so hard as part of an offshore diver's real training.
Copies and backup
The audiovisual material from a campaign takes up a lot of space and is easily lost. Procedures usually require a duplicate copy made the same day it's recorded, and periodic partial handovers to the client, rather than a single dump at the end. Losing the video of an inspection is the same as not having done it.
What this means for your career
A diver who documents well is worth more, and everyone in the industry knows it. Not because writing is the trade, but because the contractor who can deliver clean reports on time gets repeat contracts, and the one who can't argues over every monthly certification with the client.
This has a practical consequence for anyone starting out: the administrative side of the job isn't a punishment, it's a differentiator. Progression to supervisor, which requires the training described in the training guide, largely comes down to showing you can handle the paperwork, because a supervisor signs documents all day.
It's also worth keeping a clear line between what's yours and what's the client's. Project documentation isn't yours, and it's almost always under confidentiality. Your personal dive record, your medical certificates and your certifications are yours, and keeping them organised and up to date is what lets you respond within 24 hours when a agencia calls you to cover a spot. More than one contract has been lost because a piece of paper couldn't be found.
The documents that surround the work
Besides the record of what's been done, a subsea project generates an earlier layer of documentation that shapes everything else, and it's worth knowing about even though as a diver you'll rarely write it yourself.
The work procedure
Before anyone goes down there's a document describing how the task will be done: sequence, equipment, personnel, acceptance criteria and hold points. It's approved by the client, and deviating from it without written authorisation turns a job done well into a nonconforming one. When something on the bottom forces a change of method, the right move is to stop, report it and get the change in writing — not to work it out on your own judgement and mention it afterwards.
The risk assessment and the permit to work
The permit to work is the document that authorises the operation at a specific time and place, with the conditions and isolations verified. It has a date, a time and signatures, and it expires. It's probably the single piece of paper that saves the most lives in this trade, and its value depends entirely on the checks it declares actually having been done.
The nonconformance log
When something doesn't go according to procedure — a tolerance out of range, a material that wasn't the one specified, a test that fails — a nonconformance is raised. It's not a punishment or a black mark: it's the mechanism that lets someone decide, with proper judgement, whether to accept it, correct it or redo it. Hiding it is what actually causes problems, because it ends up surfacing years later in an inspection, out of context and looking worse than it was.
Documentation mistakes that cost money
There's a handful of failures that repeat across projects of every size, and it's worth being able to recognise them.
Video without a data overlay is the most costly, because it invalidates hours of perfectly good work: if you can't prove where and when it was recorded, it doesn't stand as evidence. The second is photography without a scale, which forces a return dive to measure something that was already right there. The third is inconsistent naming between shifts, which turns the final compilation into archaeology. The fourth is the dive log filled in from memory at the end of the day, with rounded times and generic descriptions, which loses exactly the detail that's needed later.
And the fifth, the quietest one: not backing up the day's material. A memory card that fails at the end of a campaign can wipe out weeks of evidence, and there's no way to recover it short of redoing the work with the vessel booked all over again.
The bottom line
Underwater work has one feature that sets it apart from almost any other trade: nobody can check the result with their own eyes. That asymmetry gets resolved through documentation, which is why the industry is so insistent about it. It's not distrust of the diver; it's the only way there is to turn invisible work into a verifiable asset.
Taking that on board early saves a lot of frustration. The report isn't what comes after the work. It's part of the work.
Frequently asked questions
What exactly is an as-built?
It's the documentation that shows how the work actually ended up, as against the design, which said how it should end up. It includes updated drawings, measurements taken on site, deviations from the design and the reasons for those changes.
Why is everything recorded on a subsea project?
Because the client can't go down and check it themselves. Video referenced with time, depth and position is the proof that the work was done, of what condition the structure was found in, and of how it looked when finished. It also serves as a defence if a defect turns up later.
Who writes the reports, the diver or the supervisor?
The diver provides the observations and measurements, the supervisor consolidates the dive log, and there's usually an inspector or project engineer who compiles the final report. On small teams the supervisor takes on all three roles.
Is it worth keeping my own personal record?
Yes. Your personal dive logbook is the proof of your experience when you change employer or renew certifications, and no one else is going to keep it up for you. It's a separate document from the project report, which belongs to the client.
Can I keep a copy of the reports when the contract ends?
Generally not. Project documentation is usually the client's property and covered by confidentiality agreements. What you can and should keep is your personal dive record and your certificates.
Published 5 September 2026 · By Arthur More, professional saturation diver
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Photo: NOAA Photo Library · CC BY via Openverse