In video of the Haixun 01, it appears the Chinese had a spare pinger in the boat.

Anish Patel, president of pinger manufacturer Dukane Seacom, says it is not recommended to have a pinger near the area where you are trying to listen.

If that pinger gets wet, it will start transmitting, potentially confusing search teams.

"I wouldn't put one where I'm measuring," Patel said. "It's just not good common practice."