Isn't this what I have heard to as one of the rules of the seas? Essentially everyone within potential rescue distance makes a concerted effort to help regardless of what they were doing or heading to and veer off course to head to the person(s) needing rescue?
Not just a rule, it is a staple of International Maritime Law. From a quick English search, it appears it is codified in a number of laws in the respective countries.
Edited to add: Since I'm not a lawyer (and I don't know if this guy is), this link explains the rules:
http://www.thelog.com/askattorney/askattorney.aspx?x=96 If you do, or will ever, operate a boat, you probably want to contact a maritime attorney. No, I don't even know where "maritime law" takes effect either, so you'll have to figure that out yourself.