“Normal” boats only go in reverse when they are maneuvering, never for extended distances and at travel speeds. Unless they’re purpose built they never travel in reverse - rudders are less efficient if going reverse, propellers are as well, and hulls are shaped to reduce drag when going forward.

You’ll basically only see boats going in reverse in harbors or exceptional circumstances. In harbors, speeds are generally low and extra caution is required of all ships. For exceptional circumstances, you’ll have special ways of communicating this - specific lighting patterns, flags, horns to warn others.