It would take a lot of time, and I’m sure it would be low priority.
Attacks from the sea, into the harbor, it would be a completely different way of attacking using ships and archers and sea monsters. The harbor would require a different gatekeeper than the normal path and would also use a separate trophy system. We may have to craft ships to hold hero/ranged people/monsters ie. Hydra archer… new sea monsters only useable in these kind of attacks/ defense. A wave tower that pushes you back away from the harbor. A storm tower that rains lightning on the ships. Have it be a system where you have like three barriers. (maybe something from Poseidon) you have to beat before you get to the harborkeeper. Maybe the gods rose a few rocky spires where towers could be placed in the sea. Just a thought.