Controversial information:
Although there is nearly unanimous agreement among the Jewish and Christian scholars that this phrase refers to a trade route, a controversy nevertheless exists as to which trade route the phrase refers.

The majority view is presented by such sites as http://www.jewishvirtuallibrary.org/jsource/History/ViaMaris.htm 
[Note: this page appears to not exist anymore. ] (see map) and http://www.bibback.com/MLand-RSM5.html {broken link} (see map)

The minority view is presented by the site http://www.netours.com/2003/Dic/D36ViaMaris.htm  which is unfortunately no longer available. (see map)

Comment:
For the purposes of this document, the minority view is considered to be correct. That is, the phrase is considered to refer to part of a trade route from Tyre to Damascus which part of the route was the former northern border of ancient Israel as mentioned by Isaiah.

Additional information:
Although the minority view (about which route is referred to by the phrase "way of the sea") is considered correct for the purposes of this document, the minority view that Isaiah was referring to "Gilead" by the phrase "beyond Jordan" (in Isaiah 9:1) is nevertheless considered incorrect for the purposes of this document. For the details of this topic, see the "Comment" about the word "Bethany".

A link to each occurrence of this phrase in This Good Riddle:
1] way of the sea