Another problem is that, from the perspective of a boat, ships appear to be going slow even when they are moving at over 20 knots… and the boaters are not look far enough ahead!
A few years back I wrote an article about using AIS to avoid ships for a yachting magazine and was asked to talk the topic at meeting off offshore sailors. They were shocked when I began talking about actions to take when you see a ship at 24 vs 12 miles… So I asked them what range scales they used. Two in the crowd said they switched their radars to 6 miles, about half said they used the 3 mile scale and the rest had their radars set to 1.5 miles or less!
A couple of them even left the talk shaking their heads when I told them they might as well sell their AIS receivers on eBay (AIS-b transceivers were not FCC approved at the time) and spend the money on float coats because once a ship with a zero cpa is less than a mile away from you… they ain’t going to have time to be looking for life jackets.