Rescuers have found five more survivors of a passenger boat that sank in Indonesian waters on Wednesday, three days after it went down, Al Jazeera reported.

The KM Nurul Salsa was carrying 78 passengers and crew when it sank roughly 43 nautical miles, about 79 kilometers, from the port of Benteng on Selayar Island, south of Sulawesi. Officials have attributed the sinking to engine failure.

What is known about the toll

Forty-seven people were rescued the day after the vessel went down. The five found this weekend bring the number recovered alive to at least 52. One person is confirmed to have drowned, and at least 20 remain unaccounted for.

Those figures do not fully reconcile against the 78 said to have been aboard, which is not unusual while a search is active: passenger manifests on domestic routes are often approximate, and survivor counts are revised as people come ashore separately or are picked up by passing vessels.

That last point is the reason the search has continued this long. Survivors described staying afloat however they could. "After the ship sank, each of them saved themselves using whatever equipment or makeshift flotation they could find," said Muhammad Arif Anwar, a local search-and-rescue official.

The search

Five large ships, a reconnaissance aircraft and a helicopter have been deployed. Warm tropical water improves survival prospects considerably compared with colder seas, which is why searches in this region are pursued for days rather than hours, and why people are still being found alive on day three.

Why this keeps happening

Indonesia is an archipelago of more than 17,000 islands, and boats are not a leisure option but basic transport between them. Ferries and small passenger vessels carry people who have no realistic alternative, over long distances, often on routes with limited oversight.

The recurring causes are familiar to Indonesian regulators: ageing vessels, mechanical failure at sea, overloading beyond a boat's rated capacity, incomplete or inaccurate passenger lists, and inconsistent enforcement of safety requirements including the provision of life jackets. Sudden weather can turn any of these from a manageable problem into a fatal one.

In this case the reported cause is mechanical rather than meteorological. An engine failure far from shore leaves a vessel unable to hold its head to the swell, and a boat that cannot steer is a boat at the mercy of the sea.

Investigations into Indonesian maritime accidents typically examine whether the vessel was carrying more people than permitted and whether safety equipment was aboard and accessible. No findings on either point have been published in this case, and it would be premature to assume them.

For now the operation remains a search rather than a recovery, which is the distinction that matters most to the families waiting at Benteng.