A cold seep is an area of the ocean floor where hydrogen sulfide, methane, and other hydrocarbon-rich fluid seepage occurs.

Wang said he has conducted research in the South China Sea four times over the last 20 years, but this was the first time that he had used a domestically-produced submersible.

"The journey reminded me of Alice's Adventures in Wonderland, and I just came back from the fairyland," Wang said when he walked out of the submersible. "I am so proud of the development of our country's marine technology."