The tourist boat, the Shuanglong, was carrying 18 people on a three-hour tour at Bailong Lake in the city of Guangyuan Saturday noon.
The boat capsized at about 2:40 p.m, minutes before it was about to reach its destination, Xinhua reporters learnt.
Three adult men survived, and one rescued child was announced dead after emergency treatment failed. A total of 14 people, mostly young parents with their children, were missing.
The tragedy befell on five families who were enjoying a weekend excursion on the lake, a popular tourist site. Boat operator Zhou Piqiang, his wife and four-year-old son are also among the missing.
A spokesperson of Blue Sky rescue team said on Sunday noon that they found the capsized boat about 65 meters under the water with the help of underwater video cameras, but no sign of life was detected.
The State Administration of Work Safety has sent a work team to the site of the accident.