Not just RNLI, all mariners inc civvy, RN and BF. The UN convention on the Law of the Sea places an obligation on all mariners and governments to assist anyone in danger or distress upon the seas. No mariner would be in any doubt that a flimsy dingy with untrained crew, non existent safety and navigation equipment and overloaded with civilians was anything but a distress situation. And in my 40 plus years at sea I've never come across anyone who would ignore such a situation.