Photo by Ju Zhenhua / For China Daily

"I have been serving in the navy for 33 years, and Hua was the first to come to me for reading materials and books on the first day of arrival. The notes he had taken from those materials can pile up to at least 2 meters high," Li says.

Li says one part of the submarine once had a mechanical failure during its eight-day mission. Because no one else on the submarine was able to fix it, Hua spent 24 consecutive hours in the malfunction area, trying to fix the problem.

"The temperature was 40 C, and he just sat there, with technical drawings and five of his notebooks scattered around him. His sweating made him look like he just came out of the water. This is a scene that I will never forget," he says.

Because Hua has devoted his efforts to submarines and the ocean, he gets to spend little time with his family.

"Our relationship started in an old - fashioned way of matchmaking," says Che Lili, Hua's wife. "The matchmaker told me that he would be away at work on weekdays and we can meet during weekends, and I thought it was acceptable," she says. "However, it was not the situation at all."

Che says her husband came home only once or twice a month last year. His total days at home were no more than 30 days in 2013, she complains.