ביום ההוא יפקד יהוה בחרבו הקשה והגדולה והחזקה על לויתן נחש ברח ועל לויתן נחש עקלתון והרג את התנין אשר בים
Actually is appears that this section really should extend from Isaiah 26:20–27:6 as a unit. As a unit, this seems to mirror the New Testament’s picture of the last day, the day of judgment. The sword is the sword of his word (Ephesians 6:17, Revelations 1:16, 19:15, 21). The dragon to be defeated the devil (Revelations 12:9, 20:2, 10). (Don’t be surprised at references in Revelations—if one knows Tanakh, one finds many allusions to Tanakh in it.)
The next verse seems to build on it:
ביום ההוא כרם חמר ענו לה
“In that day as he raises up one he desires is his answer to it.”
Karl W. Randolph.