Construction ‘as near thereto as she can safely get’ was invented to address situations when without fault from either side the vessel could not get alongside her berth or dock on arrival because of permanent obstruction.
Per Lord Campbell CJ in Schilizzi v Derry (1855) 4 E & B 873 at 886:
As to the first plea: the meaning of the charter party must be that the vessel is to get within the ambit of the port, though she many not reach the actual harbour. Now could it be said that the vessel, if she was obstructed in entering the Dardanelles, had completed her voyage to Galatz.
Lord Watson in Dahl v Nelson, Donkin, and Others, (1881) 6 App. Cas.38, stated at p.57 that:
I think it may be taken as settled law, that when, by the terms of a charterparty, a loaded ship is destined to a particular dock, or as near thereto as she may safely get, the first of these alternatives constitutes a primary obligation; and, in order to complete her voyage, the vessel must proceed to and into the dock named, unless it has become in some sense "impossible" to do so.
The Athamas  1 Lloyd’s Rep. 287 per Sellers LJ at p.295:
The clause serves to mitigate the rigidity of the bargain and by the concept of a secondary destination to permit the charter-party to be performed and to prevent it being frustrated with uncertain and perhaps harsh results for one party or the other.
… The word "ambit" does not seem to fit any commercial usage and is not a strict paraphrase of the clause. As Lord Blackburn said in Dahl v Nelson, Donkin, and Others, (1881) 6 App. Cas.38, at p. 51:
…Whether the language which Lord Campbell uses is quite the most accurate to express his idea may be doubted …
In so far as "ambit" conveys the idea of a circuit, which at least one dictionary introduces, it may well have an adaptation, for the obligation to deliver at the nearest safe port may require an extension of the voyage north, south, east or west of a named port.