A quick google brought up this

The 1974 International Convention for the Safety of Life at Sea (SOLAS Convention) obliges the

“master of a ship at sea which is in a position to be able to provide assistance, on receiving information from any source that persons are in distress at sea, is bound to proceed with all speed to their assistance, if possible informing them or the search and rescue service that the ship is doing so…”3

The 1979 International Convention on Maritime Search and Rescue (SAR Convention) obliges State Parties to:

“…ensure that assistance be provided to any person in distress at sea… regardless of the nationality or status of such a person or the circumstances in which that person is found”… and to “provide for their initial medical or other needs , and deliver them to a place of safety.”4

On 1 July 2006, amendments to the SOLAS and SAR Conventions concerning the treatment of persons rescued at sea entered into force.5 The SOLAS amendments add to and clarify the existing obligations to provide assistance, adding the words: “This obligation to provide assistance applies regardless of the nationality or status of such persons or the circumstances in which they are found"

I think that might oblige state owned harbour authorities to provide shelter but where privately owned harbours stand I don't know