When operating at night, or other times of restricted visibility (such as rain, mist or heavy fog), the required navigation lights as explained earlier in the required equipment section are mandatory to be displayed. The lights will let each boater know which is the stand-on or give-way vessel and each boater should react accordingly.
During nighttime operations vision can be tricky at best, so a proper lookout and safe speed need constant attention.
During times of restricted visibility such as smoke or fog, additional sound signals are required. Both inland and international rules require that any boat underway in or near a restricted visibility area sound a warning signal every two minutes.
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