On the water, there are right-of-way rules that define who has to give way in a potential collision situation.
Here's a video showing what happens when you don't know (or follow) the rules properly.
At the start of the video, you can hear the super-tanker blasting its horn.
From what I can tell, everyone was on the windward rail and probably their view of the super-tanker was blocked by the giant pink spinnaker.
Still, I'm sure they heard the horn; I can testify from personal experience (Hi Tom!) that the horn is loud and very hard to miss.
I sure hope that guy that appears to slip off the side just before the sailboat slides around the prow of the tanker hung on and was pulled to safety...