Final answer:
Firing a cannon and floating bread down a river is usually part of a festival celebration, such as China's Dragon Boat Festival, which commemorates the poet Qu Yuan with traditional foods like sticky rice dumplings.
Step-by-step explanation:
The practice of firing a cannon and floating bread down the river is typically associated with celebrating a festival. One such event is the Dragon Boat Festival (Duanwu) in China, which remembers the poet Qu Yuan. According to tradition, people threw sticky rice dumplings into the river to prevent the fish from consuming his body after he drowned himself. Over time, this act of remembrance has evolved into a joyous celebration, including various foods and activities like dragon boat racing.