Apologies if this is answered simply elsewhere -- I haven't studied the laws of Gittin, but this question doesn't seem to be addressed in the connected mishna in Gittin 76a.
In Ketuvot, 2b, the text establishes a case -- If a man gives his wife a Gett (divorce) which only becomes valid if he does not "return" within 30 days and then, on day 30, he is stuck on the other side of a river from where they live, the Gett becomes valid. People clearly can see him and hear him from across the river (the text indicates that he, from his side "said to them Look, I have come!" and there is no response that "they can't hear him.")
So what constitutes fully returning? If he crossed the river but stayed on the river bank? Does he have to reach a specific location, or just the city limits? (the earlier formulation was "i have come" which is not the same as "returned" but this distinction isn't explored here as location isn't spoken of)