Violent and horrific death has become a fixture of wars and terror attacks around the world. Yet there can be few ways of dying more horrible than being trapped in a slender tube of metal that is resting on the seabed while you wait, as calmly as possible, for your oxygen to run out.

It must, of course, still be hoped that the international effort to locate the Argentinian submarine San Juan and to rescue its 44 members of crew will still succeed. But a senior naval official admitted yesterday that the situation was becoming critical and that the oxygen inside the hull was coming close to running out.

When the Argentinian navy lost contact with the sub eight days ago, there appears to have been some muddle and confusion in naval headquarters. In its last radio contact, the boat reported that it had suffered a mechanical breakdown and a short-circuit in its batteries. If there was anything more to the message, the naval high command is not saying.

The normal protocol is for a submarine that has any sort of systems failure to either surface if it can or else deploy a sonar buoy that will float to wave height and transmit distress signals allowing the boat to be located and a rescue mounted. Neither of these actions appears to have happened.

But a week after the San Juan disappeared, naval headquarters admitted that there had been

a “hydro-acoustic anomaly” five hours after that last radio signal. Commanders would not say if it was likely this had been an explosion. The revelation, so late in the day, has understandably angered relatives of the crew and the wider Argentinian public. The nation still hopes the vanishing of the San Juan will have a happy outcome, but with every passing hour, such expectations shrink.

Some dozen countries, including Russia, the US, Brazil, Chile, Colombia, France, Germany, Peru, South Africa, Uruguay and the UK, have sent a variety of equipment to locate the boat and then mount a rescue. Even though it now looks very much as if this incident is going to end in tragedy, there is much comfort to be taken from the fact that when Argentina was in need, even past enemies, including Chile and the UK, were prepared to put aside their differences and pitch in to help.

The task of the searchers is, however, being made altogether more difficult because it is the nature of submarine design that they should be as hard to detect as possible. The 66-meter diesel-electric sub was built in Germany 34 years ago for the Argentinian navy and underwent a major refit that was completed two years ago. It was equipped with fail-safe systems typical of all modern warships. For any of those not to have worked suggests some sort of catastrophic event. Minds will doubtless be going back to the 2000 loss of the Russian nuclear submarine Kursk and its 118 crew. An official enquiry blamed that disaster on the explosion of fuel in a torpedo.

Whatever has gone wrong with the San Juan is the stuff of submariners’ nightmares. These were brave men, even to do the work that they did in a confined space deep under water. Their agony is echoed by their waiting family and friends. While a good outcome must still be hoped for, Argentinians are now bracing themselves for the worst.