Spanish Navy Diving Accident: 12 Reported Affected as Judge Investigates Possible Gas Contamination

New reporting has substantially changed the picture surrounding the September 16 accident at the Spanish Navy Diving Centre in Cartagena. While the Navy originally confirmed eight injured personnel, an investigation published on September 22 reports that 12 were affected, ten required hospitalization, and four are in extremely serious condition. A military judge is also investigating possible contamination associated with equipment used during the training exercise.

UPDATE, September 22, 2026: This article has been substantially updated following new reporting concerning the number of personnel affected, the sequence of events, possible contamination during the training exercise, the medical condition of several officers, and a military judicial investigation.

A serious diving training accident at the Spanish Navy’s Centro de Buceo de la Armada in Cartagena has developed into a complex investigation involving conflicting casualty figures, severely injured officers, questions surrounding a cold water training exercise, and allegations that investigators encountered difficulties obtaining information.

The accident occurred on September 16 at the Navy Diving Centre in La Algameca Naval Station.

The Spanish Navy initially confirmed that eight of its personnel had been injured while an activity was being conducted in the centre’s hyperbaric complex. Two initially had a reserved prognosis, five were described as having minor injuries and being under observation, and one had already been discharged. The Navy said an investigation had been opened to determine the circumstances of the accident.

By September 18, Ministry of Defence information showed that four personnel remained in intensive care. Two had a reserved prognosis, while another two were being kept in intensive care for closer monitoring and observation. Three other personnel had been discharged that day, in addition to one person discharged on September 16.

However, a detailed investigation published by Infobae España on September 22 presents a substantially different account of what happened.

New Report Says 12 Personnel Were Affected

According to Infobae, 12 personnel were affected during the exercise rather than the eight originally announced by the Navy.

The publication reports that ten of the 12 required hospitalization and that four officers were in extremely serious condition.

These figures have not yet been confirmed in a new public statement from the Spanish Navy or Ministry of Defence.

This creates an important unresolved discrepancy.

Official and Defence sourced reporting has consistently referred to eight injured personnel. Infobae, citing its sources close to the investigation and the families involved, reports 12 affected.

Until authorities provide an updated account, Diventures considers eight injured personnel to be officially confirmed, while the figure of 12 affected remains a significant but independently unconfirmed report.

The First Divers Reportedly Developed Problems Almost Immediately

The September 22 investigation also changes the understanding of where and how the accident may have started.

Earlier Navy information said the accident occurred while an activity was being carried out in the hyperbaric complex. Some early Spanish reports went further and described a possible malfunction involving a hyperbaric chamber.

Infobae instead reports that the officers, aged between 26 and 33, were participating in an exercise in a training pool at the centre.

According to the report, the exercise was intended to simulate demanding conditions associated with deep, cold water diving.

Infobae says the first pair of divers entered the pool and developed serious problems almost immediately. Other divers and instructors reportedly recognized that something was wrong.

Additional divers then entered the water in an attempt to assist the first pair, but reportedly began experiencing similar problems themselves.

Infobae describes loss of consciousness and respiratory difficulties among those affected.

The reported sequence, in which personnel attempting to help the first divers subsequently developed symptoms, has become an important focus of the investigation.

The Spanish Navy has not publicly confirmed this detailed sequence of events.

Investigators Examine Possible Contamination

The most significant new development concerns possible contamination associated with equipment used during the training exercise.

According to Infobae, equipment was being used to cool the pool to reproduce cold water conditions.

The publication reports that the cooling equipment uses a type of gas, generally described as a halocarbon, and that investigators are examining whether a problem involving this system could have contaminated the pool environment.

Infobae further reports a theory that, if the mixture associated with the system was compromised and entered the water, divers could potentially have been exposed around the mouth area of their equipment.

This is an account reported by Infobae and should not be interpreted as an established technical explanation of the accident.

No publicly released toxicological analysis has identified a contaminant.

There is currently no official confirmation of what substance, if any, entered the pool, its concentration, how the personnel were exposed, or whether the divers’ breathing gas supply itself was contaminated.

There has also been no official finding that the cooling equipment malfunctioned.

The possible contamination therefore remains an investigative hypothesis.

Judge Requests Maintenance Records

Infobae reports that Military Judge Number 14 of Cartagena, whose court is based in Valencia, has taken charge of a judicial investigation into the accident.

According to court sources cited by the publication, investigative proceedings have begun and the initial evidence points toward an accidental cause.

The judge is reportedly examining the condition of the equipment associated with cooling the training pool and has requested maintenance records.

Those records could become important in determining whether an equipment problem, maintenance issue, contamination event, or another mechanism contributed to the accident.

No conclusion has yet been announced.

Infobae Reports Alleged Obstruction of the Investigation

The September 22 report also contains a serious allegation concerning the judicial investigation.

Infobae, citing court sources, reports that some Navy commanders allegedly created obstacles to the military judge’s attempts to investigate the accident.

The publication specifically reports that the judge considered ordering the detention of the officer commanding the centre if the alleged obstruction continued.

Diventures has not found a publicly released judicial decision confirming that such a detention was formally ordered, and Infobae does not report that the commander was actually detained.

There has also been no judicial finding establishing wrongdoing by any Navy officer.

The allegation should therefore be understood specifically as a claim attributed by Infobae to court sources, rather than an established finding.

Families Reportedly Seeking Answers

Infobae also quotes an unnamed family source who expressed concern about both the condition of the injured officers and reports that difficulties had arisen during the judicial investigation.

According to the publication, relatives want clarification about what happened during the exercise and about the circumstances surrounding the investigation.

The family comments were provided anonymously.

Serious Neurological Conditions Reported

The new report also contains significantly more serious medical information than has been released officially.

Infobae quotes a relative as saying that one officer was in an extremely serious neurological condition, described by the source as having almost no brain activity.

The publication also reports that another two officers were in medically induced comas and that a fourth remained in intensive care.

These specific medical conditions have not been confirmed through a detailed public statement from the hospitals, Spanish Navy, or Ministry of Defence.

The most recent Defence sourced information independently confirmed by Diventures stated that four of the eight officially acknowledged injured personnel remained in intensive care, with two having a reserved prognosis and another two remaining there for closer monitoring.

The more severe descriptions published on September 22 should therefore remain attributed to Infobae and its family source.

Conflicting Information About Hospitalization

Another discrepancy concerns how many personnel required hospital care.

Infobae reports that ten of the 12 affected personnel needed hospitalization.

It says three of the more seriously injured officers remained at Santa Lucía Hospital in Cartagena, while another was at Virgen de la Arrixaca Hospital in Murcia.

The publication further reports that four additional divers remained under medical observation at Santa Lucía.

This differs from the September 18 Ministry of Defence information, which said four of the eight officially acknowledged casualties remained hospitalized in intensive care and four had been discharged.

No official explanation has yet reconciled these figures.

Hyperbaric Chambers May Have Been Used for Treatment

The role of the hyperbaric complex is another important part of the developing story.

The Navy’s original statement said the accident occurred while an activity was being performed in the centre’s hyperbaric complex. Early media reports subsequently described the incident as occurring in or involving a hyperbaric chamber.

Infobae’s later reconstruction instead places the initiating event in the training pool.

According to Infobae, the centre’s hyperbaric chambers were used afterward to provide initial treatment to some of the less severely affected personnel.

The publication reports that the treatment helped address injuries including blood clots.

Diventures has not found publicly released medical documentation confirming the reported clotting injuries or establishing the mechanism responsible for them.

That medical detail should therefore remain attributed to Infobae.

Investigators will need to clarify precisely how the pool exercise, the wider hyperbaric complex, and subsequent hyperbaric treatment fit into the timeline.

Early Reports Mentioned an Immersion Syndrome

During the first hours after the accident, several Spanish media outlets reported that the personnel may have suffered what was described as an immersion syndrome.

Cartagena Diario reported that six divers were initially believed to have been seriously affected and said early information pointed toward an immersion syndrome, although the circumstances were still awaiting official confirmation.

Telecinco subsequently reported the updated Navy figure of eight injured personnel while also referring to immersion syndrome in its account.

The Spanish Navy did not confirm immersion syndrome as a diagnosis.

The term should therefore be treated cautiously.

It is also important not to automatically equate immersion syndrome with decompression sickness.

Different diving and pressure related emergencies can produce overlapping symptoms, and identifying the actual mechanism requires consideration of the dive profile, environment, breathing gas, equipment, pressure exposure, medical findings, and other evidence.

The newer reports of multiple divers developing similar symptoms in sequence, together with the investigation into possible contamination, mean that the early immersion syndrome reports cannot currently be treated as an established explanation.

A Possible Hyperbaric Chamber Failure Was Also Reported

Another early theory concerned the hyperbaric equipment itself.

Cartagena Diario reported that the initial emergency alert referred to a possible problem involving the hyperbaric chamber. The publication clearly noted that this information had not been officially confirmed.

Other Spanish reporting also referred to the possibility of gas exposure or a chamber related technical problem during the first hours after the emergency.

The Navy did not subsequently announce that a chamber malfunction had caused the accident.

The September 22 Infobae report instead focuses primarily on the swimming pool cooling system and possible environmental contamination.

At present, neither explanation has been established by investigators.

What Happens During Hyperbaric Exposure?

The original reporting surrounding the accident drew attention to hyperbaric exposure because the Navy initially described the incident as taking place during an activity at its hyperbaric complex.

A hyperbaric chamber is a pressure vessel that allows occupants to be exposed to pressures above normal atmospheric pressure.

In diving training, increasing pressure inside a chamber can reproduce some of the pressure related physiological effects of descending underwater without requiring the occupants to enter the sea. This is sometimes described as a dry dive.

Hyperbaric systems can also be used for medical recompression following certain diving injuries.

Such systems require careful control of pressure, breathing gases, oxygen concentration, temperature, communications, and operating procedures.

Potential hazards in hyperbaric environments can include inappropriate pressure changes, breathing gas contamination, abnormal oxygen exposure, mechanical failures, and fire.

These are general hyperbaric hazards. There is currently no evidence establishing that any of them caused the Cartagena accident.

The new reporting also raises the possibility that the hyperbaric chambers may primarily have been used during the medical response rather than being the location where the initiating event occurred.

Diving Symptoms Can Have Different Causes

Symptoms following diving or exposure to unusual pressure environments do not automatically indicate decompression sickness.

Decompression illness includes decompression sickness and arterial gas embolism, but divers can also experience other conditions with overlapping symptoms.

Possible alternatives can include contaminated breathing gas exposure, oxygen toxicity, barotrauma, immersion pulmonary edema, aspiration, environmental exposure, cardiac events, and other medical conditions.

This distinction is particularly important in the Cartagena investigation because several different mechanisms have appeared in early reporting.

These have included immersion syndrome, a possible hyperbaric equipment problem, an unidentified gas exposure, and now possible contamination associated with the pool cooling system.

None has been officially established as the cause.

The Spanish Navy Diving Centre

The Centro de Buceo de la Armada is the Spanish Navy’s specialist centre for military diving and underwater operations at La Algameca Naval Station in Cartagena.

The facility is involved in diver training, underwater repair, submarine rescue support, underwater search operations, protection of submerged archaeological heritage, and other specialist maritime operations.

Its capabilities include hyperbaric facilities used for training and the treatment of diving related conditions.

The centre has played a major role in Spanish Navy diving activities for decades and operates with specialist diving, medical, technical, and support personnel.

The nature of its work makes the September 16 incident particularly significant, especially as investigators examine what occurred during a controlled military training exercise.

What Is Confirmed and What Remains Unconfirmed?

Several facts are established through Navy or Defence sourced reporting.

At least eight Spanish Navy personnel were injured on September 16.

Four subsequently required intensive care.

Four of the originally reported eight had been discharged by September 18.

The Navy opened an investigation into the accident.

The September 22 Infobae investigation adds a much larger group of claims that have not yet been independently confirmed by the Navy.

These include 12 total personnel affected, ten hospitalizations, four officers in extremely serious condition, the detailed sequence in which divers reportedly became unconscious or developed respiratory problems one after another, possible contamination associated with the pool cooling system, reported blood clots, detailed neurological conditions, and allegations concerning obstruction of the judicial investigation.

The opening of military judicial proceedings is also reported by Infobae through court sources.

Many critical questions remain unanswered.

Investigators have not publicly identified a contaminant.

No concentration or route of exposure has been established.

It is not known whether the breathing gas supply itself was contaminated.

There has been no official confirmation that the cooling system malfunctioned.

It has not been established whether maintenance played any role.

The precise physiological mechanism responsible for the injuries remains unknown.

The difference between the Navy’s eight casualties and Infobae’s reported 12 has not been explained.

The relationship between the pool exercise and the hyperbaric complex also requires clarification.

Until official findings become available, contamination, equipment failure, immersion syndrome, pressure related injury, maintenance problems, or another mechanism should all remain hypotheses rather than stated causes.

Developing story: Diventures will continue updating this article as the Spanish Navy, Ministry of Defence, military judicial authorities, hospitals, or other official sources release confirmed information about the condition of the affected personnel and the cause of the September 16 accident.

Sources: Europa Press, Puente de Mando, Democrata, Infobae