You’re correct about this. I was just looking it up myself.

There is indeed international maritime law governing vessels, and they must proceed with all possible haste to distress signals. Unfortunately, there are two problems here as I understand the situation:

1. Believe it if you want to or not but - the people operating Zuckerberg’s yacht claim they hadn’t heard or noticed the distress signal at the time
2. The Coast Guard - who, importantly, the stranded skiff had initially contacted - didn’t consider their situation to be worthy of “distress” and thus Zuckerberg and his yachtspeople didn’t violate any regulations or laws

Zuckerberg’s yachtfucks apparently said that they noticed the distress signal eventually, but by the time they had, the Coast Guard had already arranged assistance for the skiff.

So, sadly, for those of us who want to see the billionaires get their comeuppances, I don’t think we’ll see it here.