Indonesia submarine tragedy: When the sea itself is the shark

People throw flowers and petals with names of the sunken KRI Nanggala-402 submarine crew members from a boat during a prayer at the sea near Labuhan Lalang, Bali, Indonesia on April 26. Photo courtsy: Antara Foto/Fikri Yusuf/via Reuters.

Despite technological advancements, air or marine calamities cannot be completely avoided. Sometimes, nature cannot be defeated.

Whenever there is a tragedy, experts try to establish its cause. It helps us equip ourselves better for similar eventualities.

On April 21, not far from Bali, a place which normally evokes happy images of holidays and leisure, Indonesian Navy’s KRI Nanggala 402 submarine vanished in the dark early morning hours. Scheduled to perform a torpedo drill at around 4 am, the 60-metre, German-made ship went down and never came back. Its last signal was from an unsettling depth of more than 800 metres (nearly 2,600 feet), way deeper than what it could survive.

Hopes of the survival of its 53 crew members evaporated when the Nanggala was found broken into three parts on the ocean floor.

As of now, investigators believe that the cause of the sinking was a monster ‘solitary internal wave’.

According to a report on Nikkei Asia, officers said that differences in the density of the water near Bali and in the nearby Lombok Strait may have generated a "massive movement" strong enough to take down the submarine in seconds.

A Japanese weather satellite, Himawari 8, had images that confirmed the presence of the wave near the submarine, said Iwan Isnurwanto, commander of the Indonesian Navy Staff and Command School.

"There was nothing that they could do, no time to do anything... if the sub was brought down by such a wave,” Isnurwanto said in a press conference. “It likely angled [downward], causing all the crew members to roll down [to the bottom of the vessel]. We have to do further investigation, but that is most likely what happened."

What is the scientific definition of an internal solitary wave? According to nature.com, these are “hump-shaped, large-amplitude waves that are physically analogous to surface waves except that they propagate within the fluid, along density steps that typically characterize the layered vertical structure of lakes, oceans and the atmosphere. As do surface waves, internal solitary waves may overturn and break, and the process is thought to provide a globally significant source of turbulent mixing and energy dissipation. Although commonly observed in geophysical fluids, the origins of internal solitary waves remain unclear.”

As of now, better detection of waves is the only protection underwater operations have against them.

An old video has emerged of the Nanggala crew singing the Indonesian song ‘Sampal Jumpa’. It means ‘Till we meet’. But the treacherous ocean had other plans for the sailors.