How much of the offshore estate is beyond diver depth?

Forty-one per cent, and that is the generous reading

The platform directory holds 87 offshore production structures: fixed platforms, tension-leg platforms, spars, semi-submersibles and production ships. Of those, 85 publish a water depth. The other two do not, and a blank in a directory is a blank, not a zero — we have no idea how deep they sit, and we have not guessed.

Among the 85 that do publish a figure, 35 sit in 300 metres of water or less. Fifty sit deeper. The median is 500 metres.

The 300-metre line is not arbitrary. It is the deepest depth rating published by any saturation system in the dive support vessel fleet we audited, which means it is the outer limit of where a bell can physically be put — and in practice almost nothing works at the extreme of its rating. We have written separately about why the fleet stops at 300 metres and what the 46 vessels in the dive support vessel directory are actually rated to. Take 300 metres as the theoretical ceiling and the picture is that 41.2% of the offshore estate in our directory is reachable by diver at all. Take a more realistic working ceiling and the share falls further, though we cannot put a number on that from the directory.

Read it as a curve, not an average

A median is a single point and it hides the shape of the distribution. What the depth data actually looks like is a curve: for each depth, what share of the platforms are at that depth or shallower. The chart below is that curve, and the useful way to read it is to pick the depth your equipment can reach and read off how much of the estate that buys you.

The numbers behind the curve are worth reading slowly. At 50 metres — ordinary air-diving territory — you have reached 8.2% of the platforms. At 100 metres, 14.1%. At 200 metres, 35.3%. At 300 metres, 41.2%. At 500 metres, 50.6%. At 1,000 metres, 57.6%. At 1,500 metres, 77.6%. At 2,000 metres, 90.6%. The last platforms are accounted for at 3,000 metres.

Two features stand out. The first is how much of the curve is spent between 100 and 200 metres: the share more than doubles across that band, from 14.1% to 35.3%. That is the classic continental-shelf band — the Persian Gulf, the southern and central North Sea, the shallow Gulf — and it is where the historical air- and mixed-gas diving industry was built. The second is the flat stretch that follows. Between 300 metres and 1,000 metres the share only moves from 41.2% to 57.6%, and then the curve climbs steeply again to 90.6% by 2,000 metres. The likeliest reading is that there is no meaningful population of platforms in the 500-to-1,000-metre band: engineering pushes structures either onto the shelf or out to genuine deepwater, and the middle is thinly occupied. We cannot prove that from 85 records, but the shape is hard to read any other way.

Either way, the consequence for diving is the same. The band a bell can work in is the left-hand third of that curve, and the curve does most of its climbing to the right of it.

The shallow end is a short list

If you want to know where diving work on platforms is concentrated, the honest answer is that it lives in a very small slice of the directory. Twelve platforms sit in 100 metres of water or less. Seven sit in 50 metres or less. That is the part of the offshore estate where a diver is not merely possible but routine — where surface-supplied air and light mixed-gas work is the normal way to get a job done, and where a saturation spread would be overkill.

The ten shallowest structures in the directory make the geography obvious.

Source: satdiver.com offshore platform directory, read 28 September 2026.

The Persian Gulf dominates the list, with the Caspian, the Russian Far East and the North Sea filling out the rest. Not one entry is in the Gulf of Mexico or off Brazil. Kashagan, in four metres of water, is an extreme case — it is an artificial-island development in a sea that freezes — but the pattern holds across the rest: the shallow-water estate is enclosed and semi-enclosed seas, and it is old. Ekofisk and Sleipner A are North Sea fields whose infrastructure long predates the deepwater era, and they are the shallowest North Sea entries we hold.

That has a practical reading for anyone weighing up where air-diving work is. It is not spread evenly across the offshore world. It is in the Gulf states, the Caspian, and the older parts of the North Sea. Our comparison of the North Sea against the Gulf of Mexico makes the same point from the vessel side.

The ten deepest are in a different business

At the other end of the directory the depths stop being a diving question at all. The chart below plots the ten deepest platforms we hold, and the thing to look at is not the ranking but the axis — every bar is several times the outer rating of any saturation system in the fleet.

Stones, in the Gulf of Mexico, is the deepest structure in the directory at 2,900 metres. Perdido follows at 2,450 metres and Appomattox at 2,200 metres, both also Gulf of Mexico. Then the list crosses to Brazil: P-66 at 2,150 metres and FPSO Cidade de Angra dos Reis at 2,140 metres. Atlantis, Na Kika and Jack/St. Malo are back in the Gulf of Mexico at 2,130, 2,100 and 2,100 metres. P-74 and P-75, both Brazilian, close the list at 1,980 metres each.

Every one of the ten is either Gulf of Mexico or Brazil. This is the pre-salt and the deepwater Gulf, and it is a subsea business: the wells are on the seabed, the trees and manifolds are installed and intervened by vessel and ROV, and the floating structure on the surface is tied to them by risers and umbilicals. There is no version of this work in which a diver goes to the wellhead. Whatever hyperbaric work exists on these fields is at the top of the water column — hull, mooring, turret, riser upper sections — not at the reservoir.

What this does and does not mean for diving work

The temptation is to read 50 platforms beyond 300 metres as 50 platforms with no diving. That is too neat. Even on a floating production unit in 2,000 metres of water there is steel in the first 50 metres of the water column: hull plate and anodes, fairleads and mooring chain in the splash and upper zones, riser hang-offs, turret bearings and seals on a production ship, caissons and sea chests. Some of that is inspected by ROV and some of it is not, and where access is awkward and the tolerance for damage is low, a diver is still the tool. What has changed is the nature of the job: it is maintenance of the top of the structure rather than construction and intervention at the bottom of it.

The second thing the depth data does not tell you is how much work there is. A directory of 87 platforms is a list of assets, not a list of scopes. It says nothing about inspection intervals, tie-back campaigns, decommissioning programmes or how many diver-days any of these structures generates in a year. We hold 80 platforms recorded as active and seven in decommissioning or removal, and decommissioning is one of the few areas where shallow-water diving demand plausibly grows rather than shrinks — but seven records is too small a base to build an argument on, and we are not going to.

What the data does support is a directional claim about where the industry's centre of gravity sits. The median platform in our directory is in 500 metres of water. The industry that installs and maintains structures at that depth is a subsea-engineering industry, and the diving part of it is the specialised, expensive, saturation part rather than the volume air-diving part. That is consistent with what we found on the supply side: saturation capability is concentrated in a handful of operators, and we counted the 17 companies that run saturation out of the 876 in the directory. If you are deciding what to train for, it is worth understanding what saturation diving actually is before assuming that deeper water means more diving jobs. Mostly it means fewer, held by fewer people.

How we counted this

We read every record in satdiver's offshore platform directory on 28 September 2026 and took the water-depth field as published. There were 87 records; 85 carried a depth and two were blank. All percentages, the median and the cumulative curve are computed over the 85 records with a depth, not over all 87. The counts of platforms at or below a given depth — seven at 50 metres or less, 12 at 100 metres or less, 35 at 300 metres or less, 50 above 300 metres — are simple counts of those 85.

The obvious limit is that this is a directory of notable offshore platforms, not a census of the world's offshore structures. There are thousands of fixed platforms in the Gulf of Mexico, the Persian Gulf and the Gulf of Thailand alone, most of them small, shallow and unremarkable, and almost none of them are in here. A census would look markedly shallower than our 85 records do, and the 41.2% figure would rise. What our directory is good for is the significant, named, individually documented estate — the structures that get written about, photographed and worked on by international contractors — and within that set the deep bias is real and is the point.

Other limits worth stating. Depths are as published by operators and in public documentation; some are rounded to the nearest 50 or 100 metres at source, which is why the curve has flat steps in it. A depth figure can refer to the design depth of a structure or the actual depth at its installed location, and we cannot always tell which. Production ships and semi-submersibles are included alongside fixed structures, which is defensible for a depth analysis but means "platform" is doing a lot of work as a word. Regions are our own grouping, not an operator's. And the active-versus-decommissioning split reflects what was published at the time of reading, which changes faster than a directory does.

Finally, nothing here measures diving. We are inferring reachability from water depth and from the fleet's published depth ratings. We do not know how many of the 85 platforms have had a diver on them this year, and the directory cannot tell us.

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