Would one receive a bill in a situation like this? To cover the cost of lost time and/or extra diesel burned? Or is it purely out of the goodness of the hearts of the management of the towing vessel?
All vessels have an international duty to give reasonable assistance to other ships in distress in order to save life, but there is no obligation to try to salve the vessel. Any offer of salvage assistance may be refused; but if it is accepted a contract automatically arises to give the successful salvor the right to a reward under the 1989 Convention.