“Before I went there, I couldn’t understand how isolated you were,” she said in an interview on the back deck of the Equator after it arrived in Fremantle, the port that serves Perth, Australia, to pick up supplies in early May. “We didn’t see any other vessels for weeks.”

The Fugro Equator has repeatedly found fields of debris on the deep ocean floor, 12,000 to 15,000 feet below the waves. Each time, spirits have soared as the crew members hoped that they had found the missing plane.

The first time they found a debris field, they were so excited that Fugro even notified the office of Prime Minister Malcolm Turnbull of Australia, who was traveling in Europe, to be ready to make an announcement.

Each time, the Equator or one of the other vessels has sent down an unmanned, remotely operated device to examine the wreckage with very high-resolution sonar and sometimes with cameras as well. But every time, the debris has turned out to be from previously unknown shipwrecks.