Possible Clues:

• Thriller set in the seaside town of Amity
• Chats
• 1975 film with the line 'You're gonna need a bigger boat'
• Whence comes the misquote 'We're gonna need a bigger boat'
• Spielberg thriller set on Amity Island
• It reportedly had an impact on beachgoers in 1975
• Scary film talks
• Thriller partly set aboard the Orca
• Film that justified all water safety principles
• 1975's top-grossing movie