Can the captain of a river boat be changed at any time?

I can't. According to "People's Republic of China (PRC) River Ship Crew Rules", only when the captain can't perform his duties, or when the captain unexpectedly disappears or dies, can he be replaced, and he can't be replaced at any time. There are relevant provisions in the Rules of Crew Duty and the safety management systems of various ship management companies. That is, body double, whose first mate is the captain.