The word "patience" is a metonym for God himself. Peter writes of God's patience as if it is a person. Alternate translation: "when God was waiting patiently" (See: [[rc://en/ta/man/translate/figs-personification]] and [[rc://en/ta/man/translate/figs-metonymy]])
This can be stated in active form. Alternate translation: "during the time of Noah, when he was building an ark" (See: [[rc://en/ta/man/translate/figs-activepassive]])