In the very hard difficulty, it is impossible to become the King of the ocean as highly recommended by many strategy guides. In those forced auto-resolves, the AI always win even if the odds are 1 (AI) : 2 (human).

The way to work around is: building a series of ports along the coast as "jump points" for transporting army. Since the AI never attacks ships docked inside a port, every turn we can move a fleet to the next port for protection. We can also ocassionally drive away a lone AI fleet or two, but the casaulty is very disproportional.

The AI always build tons of fleet and relatively little land troops. I would rather invest the upkeep on land armies to smash out their castle and nullify their navy at once.