A shipwreck is a catastrophe for those involved, but for historians and archaeologists of future generations it is an opportunity.
Wrecks offer glimpses not only of the nautical technology of the past but also of its economy, trade, culture and, sometimes, its warfare.
Until recently, though, most of the 3m ships estimated to be lying on the seabed have been out of reach. Underwater archaeology has mainly been the preserve of scuba divers.
That has limited the endeavor to waters less than 50 meters deep, excluding 98% of the sea floor from inspection.
Even allowing for the tendency of trading vessels to be coasters rather than ocean-going ships, that limits the number of wrecks available for discovery and examination.
Moreover, shallow-water shipwrecks are often damaged. Storms reach down to affect them. Seaweeds and corals, which need light to grow, colonize them.
Freelance divers, seeking salvage rather than knowledge, despoil them. Archaeologists do sometimes team up with people who have access to miniature submarines (some manned, some unmanned) to explore deeper waters.
But such expeditions are expensive—a million dollars a pop is not untypical—and archaeology is not a well-resourced profession. Often, these expeditions are privately financed, speculative ventures which amount to little more than treasure-hunting.
Modern robotics, however, is changing this. A new generation of cheap, free-swimming, automatic underwater vehicles (AUVs) is being developed. Past minisubs have needed a lot of backup and, if unmanned, have had to be guided by signals passing down tethers.
Their mother-ships have thus had to be fitted out specially, which is one reason for the expense. An AUV, by contrast, can be dropped into the ocean and left to fend for itself. A wider range of vessels can thus support it.