The sea battle is at the very bottom of the list. It's the only major battle scene that they've filmed that I don't think worked all the way. It's edited frantically, has some fake looking fire particle effects, has a goofy setup (how did Euron's entire fleet even sneak up on them and pick out the single ship carrying everyone of importance), and it doesn't contain many characters anyone gives a shyt about.
But worst of all, it's not even a proper sea battle. For a group of sea faring war pirates, not getting to see them properly duke it out at sea was a letdown. Budget and time restraints probably, but yeah, bottom of the list for me.