As regards US Maritime law, I can offer this -
Copy and pasted from http://www.maritimeinjurylawyersblog.com/2013/02/rescues_at_sea_the_united_stat.html
According to federal law, 45 USC Section 2304, the master of a vessel must aid anyone at sea who is in danger of losing their lives, as long as such rescue can be performed without serious threat to the master, the master’s vessel, and those on board. However, maritime law is in agreement with common law in that an individual, including a vessel master, has this statutory duty to assist those in peril at sea only when a certain relationship exists, such as carrier/passenger, vessel/seaman, and employer/employee; also, whoever has caused a danger at sea must aid any persons or property they have endangered. Further, whether because of an established relationship or as a Good Samaritan, if an individual attempts a rescue which results in further harm due to negligence, recklessness, or wantonness, he or she may be held liable for damages.