In this viral video of two vessels colliding, there is a failure both in terms of keeping a proper lookout and adhering to the Rules of the Road.
Regardless of whether you're the stand-on or give-way vessel, skippers must do whatever is necessary to avoid a collision. And never assume that the skipper of an approaching vessel sees you.
Mobile users: watch the video on YouTube.
For the Rules of the Road, visit the Coast Guard's Navigation Center.