Underwater berth maintenance means inspecting and repairing the submerged part of fenders, piles, sheet piling, caissons and their anchorages. It's carried out by the surface-supplied commercial diver, almost always with the quay in service, and the real difficulty lies in working in poor visibility next to manoeuvring vessels.
A quay is a structure that works by taking hits. Every berthing transmits to the waterfront the energy of a ship arriving with momentum, and that energy is absorbed by specific components: the fenders, their anchorages and the structure that holds them. Half of that assembly sits permanently underwater, where nobody looks at it.
The result is that berth maintenance has a visible part, handled from land with an elevating platform, and a submerged part that can only be assessed by putting someone underneath. That second part is commercial diving work, and it supports a notable number of civil and inland diving professionals, a world away from the popular image of saturation diving.
It's a stable niche, with recurring clients — port authorities, private terminals, industries with their own quay — and the advantage that the work is close to home. It's also a niche where coordination mistakes come at a high price, because the work happens in a space shared with moving vessels.
What's underwater at a berth
Before getting into inspection, it's worth being clear on what gets checked, because each element degrades differently and calls for different repairs.
Fenders and their anchorages
The fender is the sacrificial element: it absorbs berthing energy by deforming. It can be a rubber block, a cylinder, a panel with a face pad, or a pneumatic fender. What fails most often isn't usually the rubber itself, but the connection: anchor bolts, weight and tension chains, and the eye plates embedded in the concrete. A snapped bolt doesn't show from above and leaves the fender working under false conditions, passing on to the structure a load it wasn't designed for.
Piles, sheet piling and caissons
Underneath there's a load-bearing structure that usually falls into one of three families: concrete or steel piles, driven steel sheet piling forming a wall, or concrete caissons resting on a bedding layer. The diver checks section loss in the metal, cracking and spalling with exposed reinforcement in the concrete, open joints between caissons and the condition of the bedding layer.
Elementos auxiliares
Emergency ladders, thimbles, low bollards, service pipework running under the quay, and anchorages for floating pontoons. They're minor items in the budget but matter for safety, and they get checked in the same campaign because the diver is already in the water.
How the submerged part degrades
Corrosion and the splash zone
In metal structures the critical point is almost never the bottom: it's the tidal and splash zone, where water and air alternate and corrosion speeds up. Below that, in permanent immersion, the metal degrades more slowly and is usually protected by coating and anodes. That's why an inspection that only looks at the deep part misses exactly the zone that's in the worst state.
Impact, fatigue and misalignment
Berthing impacts gradually loosen fasteners, oval out bolt holes and fatigue chains. A common symptom is a fender that has rotated or dropped from its original position: it's still there, but it no longer takes the hit where it should. The diver measures and photographs the actual position against the design position, and that comparison is often the most valuable finding of the campaign.
Bed scour
Ships' propellers, especially thrusters, move material on the seabed next to the quay. Over time this can undermine the base of a caisson or expose the tip of a pile. It's detected by comparing soundings and profiles with those from previous campaigns, not by looking at a single photo.
How the inspection is organised
The normal approach is to work in levels. A first level of general visual inspection over the whole surface, cleaning only as much as needed, to locate suspect areas. A second level of detailed inspection on those specific areas, which calls for cleaning the fouling down to the substrate to be able to really see and measure. It's the logic of underwater visual inspection aplicada a obra portuaria.
Pre-cleaning isn't a minor detail: in warmer waters, biological growth can completely hide a crack or a loss of section. It's done with pressure water or mechanical tools, and it takes up a good part of the campaign's time.
Visibility governs the whole method. In many commercial ports the water is turbid from traffic and suspended sediment, so the diver navigates by feel and by fixed references: vertical guide lines, pile numbering, draught marks. Video and photography are still taken, with the camera pressed against the element and its own light source.
What repairs get done without taking the structure out of the water
A significant part of the work is done underwater without resorting to cofferdams or dry-docking. Replacing fasteners and fender chains is the most frequent job and is done with hydraulic tools. Concrete repair with exposed reinforcement is tackled with formwork filled with mortar or specially formulated concrete, and for corrosion protection the anodes of the cathodic protection.
system are replaced or extended. On metal structures, pile jacketing is also used: a sleeve is fitted around the damaged member and the annular space is filled, restoring section and isolating the metal from the environment. It's a widely used solution because it doesn't require stopping the terminal.
What's rarely resolved underwater is a repair with high structural demands on welding. There, it's assessed whether a dry intervention pays off, and that decision isn't made by the diver: it's made by the owner and their engineers, based on the inspection report.
The real risk: sharing the water with ships
The dominant hazard in this work isn't depth, which is usually modest, but the operating environment. A ship starting up a thruster a few metres from a diver generates a current strong enough to sweep them away and foul the umbilical. An approaching tug, a mooring line that suddenly takes up load, or a discharge from a scupper are just as everyday as they are dangerous.
Control rests on formal coordination, not goodwill. Before the dive, a work window is agreed with the terminal and the port authority, nearby vessels are notified by radio, any equipment that could start up is locked out and tagged — including the thrusters of the berthed ship, if there is one — and the area is signalled. The permit to work is the document that ties all of that together, and without it nobody goes into the water.
The second specific risk is differential pressure where there are active intakes or discharges. An open scupper or suction point can pin a diver against the grating with a force that can't be overcome by pulling on the umbilical. It's identified beforehand, locked out beforehand, and checked in the water.
On top of that come the site conditions: water quality at ports with industrial activity, which can call for isolation gear; confined spaces under pontoons and between caissons; and sharp objects on the bottom. None of this is exotic, and that's exactly why it gets taken lightly.
What the diver delivers at the end of the campaign
The product of a berth inspection campaign isn't the dive, it's the report. And a useful report has a recognisable structure: an inventory of the elements checked with their identification, the condition of each with the evidence backing it up, comparison with previous campaigns where they exist, and a prioritisation of actions separating what's urgent from what can be scheduled.
That prioritisation is the part the client values most and the part most often skimped on. Saying a pile has exposed reinforcement is an observation; saying over what length, how far it extends, whether it has progressed since the last inspection, and whether it affects how the berth is operated is information you can actually decide on. Anyone with a camera can do the first; the second calls for judgement and method.
That's why it's worth agreeing beforehand what format the owner expects, what nomenclature they use to identify their elements, and what level of detail they need. A technically flawless campaign that delivers a three-hour video with no references is useless, and that conversation happens at the start, not at handover.
Who does this work and how to get into it
It's carried out by the surface-supplied commercial diver holding whatever qualification the country where the job is located requires. There's no need to go through saturation certification, and in fact most people who do this work neither have it nor need it. The usual way in is to train at a recognised school and look for work with marine construction and port services companies.
What sets a good professional apart here is less dramatic than people imagine: the ability to work in zero visibility without losing orientation, judgement about what's actually worth cleaning and measuring, and above all, discipline in documenting. The client isn't buying dives, they're buying a report they can use to decide where to spend their maintenance budget.
It's also a good school of method. Anyone who learns here how to prepare a permit to work, coordinate with a terminal, and write a defensible report arrives better prepared for any other niche, including offshore. You can see which companies operate in this segment in the listing of commercial diving companies.
Frequently asked questions
Do you have to stop the terminal to inspect a quay?
Not in most cases. It's normal to work with the terminal in service, agreeing windows by section and coordinating each dive with vessel traffic. The operation only stops when the repair requires it or when it can't be guaranteed that no ship will manoeuvre near the diver.
What breaks most often on a quay fender?
The connection, before the rubber. Anchor bolts, weight and tension chains and embedded eye plates are the elements that fail most, because they accumulate impact fatigue and corrosion. A fender can look intact from the quay and still be working under false conditions because it's lost an anchorage.
Can concrete be repaired underwater?
Yes. Deteriorated concrete is cleaned back to sound material, the reinforcement is treated if it's exposed, formwork is placed around the piece and it's filled with mortar or with concrete formulated for placement in the presence of water. It's an established technique in port construction.
How deep does this work go?
It depends on the berth's draught, but it usually falls in a modest range compared with offshore work. The difficulty doesn't come from depth but from visibility, current, and working next to manoeuvring ships.
Is this a good niche to start out in commercial diving?
It's one of the most realistic ways to get started in many countries, because demand is local and recurring and doesn't require saturation certifications. It also offers solid training in work method, coordination and documentation.
Published 6 September 2026 · By Arthur More, professional saturation diver
Photo: rmlowe · CC BY via Openverse