The text is not clear if Paul took a ship to Athens or travelled there by land. Perhaps his pursuers did not know either. It seems that Paul"s escorts took him to the sea to give the impression that they intended to put him on a ship, but then they accompanied him to Athens by land. [1] In any case he reached Athens, 195 miles south-southwest of Berea, safely and sent instructions back with the Berean brethren who had accompanied him that Silas and Timothy should join him soon. They apparently had stayed behind, or been sent back, to confirm the new converts ( Acts 18:5). They appear to have rejoined Paul in Athens as he requested (cf. 1 Thessalonians 3:1). [source][source][source]
"Then Timothy was sent back to Thessalonica ( 1 Thessalonians 3:2). Silas, however, seems to have gone back to Macedonia (cf. Acts 18:5)-probably to Philippi, where he received from the young congregation there a gift of money for the support of the missioners ( Philippians 4:15). In the meantime, Paul had moved from Athens to Corinth ( Acts 18:1) and was joined there by Silas and Timothy on their return from Macedonia ( Acts 18:5; 1 Thessalonians 3:6)." [2][source]
Thus Luke"s account of Paul"s evangelizing in Macedonia concludes. From there the gospel went south to the neighboring province of Achaia. [source][source][source]