The Navigation Rules require a proper lookout by sight, hearing and all available means. CPA and TCPA estimates normally assume constant courses and speeds and can change immediately when either vessel maneuvers.
AIS may be absent, delayed, incorrect or carried by only some traffic. Small craft, paddlers, debris and navigation aids may not appear as targets.
Use electronic tools to support—not replace—visual scanning, radar where fitted, safe speed and early action under the Rules.