Who are the Titanic sub passengers?: A Titanic expert, an adventurer, a CEO, and a father and son

Rescuers were racing against the clock because the oxygen supply could run out by approximately 6am Thursday (midday Irish time).

Passengers on the missing sub (clockwise from top left): Paul Henri Nargeolet; Shahzada Dawood and his son, Sulaiman Dawood; Stockton Rush; and Hamish Harding.

A renowned Titanic expert, a world-record-holding adventurer, two members of one of Pakistan’s wealthiest families and the CEO of the company leading an expedition to the world’s most famous shipwreck are facing critical danger aboard a small submersible that went missing in the Atlantic Ocean.

The submersible Titan was reported overdue Sunday night about 435 miles (700 kilometers) south of St. John’s, Newfoundland, according to Canada’s Joint Rescue Coordination Center, spurring a desperate international rescue effort.