We don't have synonyms for boat neck yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are boat deck and boatneck.
(N) :
A boat neck, also called a bateau neck or Sabrina neckline, is a wide neckline that runs horizontally, front and back, almost to the shoulder points, across the collarbone.
(N) :
A boat neck, also called a bateau neck or Sabrina neckline, is a wide neckline that runs horizontally, front and back, almost to the shoulder points, across the collarbone.