The point of Jesus' parable about the Good Samaritan (Luke25) was found in the fact that Samaritans and Jews were enemies. Yet while no fellow Jews, not even a priest, would come to the injured man's aid, a Samaritan did. The moral: Give aid to your enemy in his time of need, this is what good people do.
But in today's world, the Good Samaritan would almost certainly have been sued, perhaps prosecuted, even beat up or shot for that matter. We live in a very sick society. I'm not saying I wouldn't render aid to an unattended boat, I would. But I'd be very, very careful about it if there were witnesses or cameras. As was mentioned, the dock master, fleet captain, marina office, even law enforcement would be tried first.
There have been folks sued for giving CPR, for crying out loud. It's madness.