What came out of the Solent in October of 1982 was half a ship.
Not half a ship because something went wrong on lift day. Half a ship because half was all there was. The Mary Rose went down in July of 1545 and settled onto her starboard side. Silt came in behind her and packed, and within a few decades the starboard hull was sealed inside anaerobic mud. The port side stayed up in the water: oxygen, current, and everything that eats wood. By the time the wreck was located again in 1971, the port side had been gone for centuries.
Same ship. Same water. Same four hundred and thirty-seven years. One half preserved well enough that you can still read the carpenters' marks, the other half erased so completely that nobody has ever seen it. The difference was a few feet of silt.
I want to be careful about the conclusion people in my industry usually draw from that story, because they usually draw the wrong one.
In situ preservation is right, and it is not sentimental
The Annex to the 2001 UNESCO Convention names in situ preservation the first option for underwater cultural heritage. That rule is sound, and I would vote for it. It is also not a moral preference. It is a statement about physics and biology that happens to be true.
Burial in fine sediment cuts off oxygen, and without oxygen most of what destroys a wreck simply stops. Cold slows everything further. Low salinity does something more specific: Teredo navalis, the shipworm that reduces exposed timber to lace, needs salt water to live, and the usual figure given is somewhere around eight or nine parts per thousand. Much of the Baltic sits below that. Which is why the Vasa came off the bottom of Stockholm harbour in 1961 as a ship rather than a stain, three hundred and thirty-three years after she sank on her maiden voyage in front of a crowd.
No conservation laboratory on earth has ever matched what that water did for free. That is the case for in situ preservation, and it is a strong one. It is the most effective preservation method in the history of the field, and its operating cost is zero.
But it is a condition, not a decision
Here is the part that the Mary Rose makes impossible to argue with. Both halves of that hull were preserved in situ. Identical policy, identical site, opposite outcomes. The policy did not preserve the starboard side. The mud did.
And mud moves. A storm can strip in one night a site that was buried for three hundred years, and from that morning the clock runs differently. Salinity is not fixed either, which is why the reported spread of Teredo navalis into the southwestern Baltic is treated as an emergency by the people who know those wrecks best. They are not being dramatic. If the shipworm establishes there, the thing that preserved that region's wrecks stops preserving them, and no rule in any convention will slow it down. Bottom gear works the seabed. Sediment migrates. Anodes fail and iron goes on corroding.
So in situ preservation is not a decision a committee makes once and files. It is a physical state that a given site is either in or not, and the state changes.
The counterargument, and it is pointed straight at me
Everything above is precisely the argument that a commercial recovery operation has the greatest incentive to make.
"The site is deteriorating" is the oldest justification in this business. It has been used to open sites that were stable, by operators whose real interest was the cargo, who produced no measurements before and none after, and who left nothing behind that anyone could check. That history is real, it is recent, and it is why an archaeologist reading a company's urgency claim should treat it as motivated until it is evidenced.
That reflex is not obstruction. It is the discipline doing its job, and I would apply the same discount from their side of the table. I apply it from this side.
Which means the argument cannot be won by asserting decay more loudly. It can only be settled by measurement, and that leads to the question in the title.
The question almost nobody funds
Who is actually watching the site?
For a small number of famous wrecks, someone genuinely is. There are sites with named custodians, repeat surveys, instrumentation, and a real record of how conditions have moved over decades. That work is excellent and the people doing it are underpaid.
For the overwhelming majority of recorded wrecks, the honest answer is that nobody has been back, nobody is scheduled to go back, and there is no line in anyone's budget to send them. This is not a failure of the discipline. It is the arithmetic from No. 002 aimed at a different target. Monitoring produces no artifact, no exhibition, no headline, and no revenue. It is a vessel, a survey spread, and a crew, burning days at full rate to generate a number that ideally reports that nothing has changed. Try writing that grant.
Where those five things exist, in situ preservation is preservation, and it will beat anything this company could do with the object. Where none of them exist, the phrase has quietly changed jobs. It is now describing a site that is unwatched and unprotected, and calling that protection.
The bill this comes with
If that is the real gap, then it is not enough for the company to point at it. The obligations run this way, and they are meant to cost us.
Treasure Experience surveys more seabed than it will ever excavate, which means it generates condition data on sites it has no interest in. That data belongs with the permitting authority: handed over whether or not a permit follows, whether or not the authority asked, and whether or not the site is one anybody here wants. It is worth nothing to us and it is somebody's baseline.
The return trip gets funded on sites the company surveys and does not touch. Those are days on the meter that produce, at best, the finding that nothing has changed, and that is the finding worth paying for.
No urgency claim leaves this building without the measurements underneath it, published in a form that a critic can check and contradict.
And the verdict gets accepted when it goes the other way. A site that is deeply buried, anoxic, stable, and unvisited is already being preserved better than we could preserve it, and the correct action is to record it, report it, and leave it alone.
That last one is the only line here that can ever cost us a season. So that is the one to hold us to.
In situ is not a promise the sea makes. It is a condition somebody has to go back and measure.