Waterdeep: War on Water?

[Unoriginal]

I know the answer is ultimately "whatever you decide as a DM", but I'm off the books right now and am trying to figure something that is logical.

Let's say someone wanted to attack Waterdeep, as presented in Dragon Heist, by the sea, what forces would oppose them?

It doesn't seem to me Waterdeep has a particularly strong navy, and given they're in a rather well-protected bay, it'd make sense they would wait until the enemy's fleet is in view, have cannons, catapults and other siege engines rain death on them from the shores, followed by their high-level magic users when the enemy boats are close enough of each other, and then finishing them off with arrows and less powerful spells if the enemy gets really close. Meanwhile, their actual naval forces would probably be mostly composed of the city's soldiers and people from the Order of Magisters loaded in transport or requisitioned civilian ships, helped by the sailors and "privateers" from the dock ward, along with whatever mercenaries, adventurers or aquatic beings that agreed to join the fight.

I'm mostly trying to figure out how well-defended against such an attack Waterdeep would seem, for a well-informed outsider.

[ProsecutorGodot]

Waterdeep has fortified walls across the entire coast and the actual bay that the harbor sits in is pretty well fortified with 2 island outposts.

You'd be hard pressed to get anywhere near the coast of Waterdeep (except via submarine, which do exist) without someone noticing your approach. You might honestly be in more trouble if you decided to try and enter via submarine, there are some pretty unfriendly things in the ocean around Waterdeep. The Mud Flats on the west side is notable for having the least amount of stationed guards.

The statues of Waterdeep could also venture into the ocean to defend against a large enough threat, which has happened in the past. There's also the Griffon Cavalry, which would be able to interpose themselves at sea or land. The Order of Magists and protectors could fly out and cause havoc against any would-be pirate. That's ignoring if any of the big wigs decided to get involved like Elminster, Laeral Silverhand or Vajrah Safhar, all of whom are powerful beyond the level of an Archmage.

The short answer is that you'll not fare much better by sea than you would by land or even by sky. There's a good reason the city is as developed as it is.

[Unoriginal]

Waterdeep has fortified walls across the entire coast and the actual bay that the harbor sits in is pretty well fortified with 2 island outposts.

You'd be hard pressed to get anywhere near the coast of Waterdeep (except via submarine, which do exist) without someone noticing your approach. You might honestly be in more trouble if you decided to try and enter via submarine, there are some pretty unfriendly things in the ocean around Waterdeep. The Mud Flats on the west side is notable for having the least amount of stationed guards.

The statues of Waterdeep could also venture into the ocean to defend against a large enough threat, which has happened in the past. There's also the Griffon Cavalry, which would be able to interpose themselves at sea or land. The Order of Magists and protectors could fly out and cause havoc against any would-be pirate. That's ignoring if any of the big wigs decided to get involved like Elminster, Laeral Silverhand or Vajrah Safhar, all of whom are powerful beyond the level of an Archmage.

The short answer is that you'll not fare much better by sea than you would by land or even by sky. There's a good reason the city is as developed as it is.

True, but I'm mostly seeing if it's be seen as a challenge or a suicide by someone with a big fleet

I guess the Walking Statues would be seen as the most dangerous threat, so... sending assassins after the Blackstaff would probably be a priority.

You're right, though, the only way in which Waterdeep is even slightly vulnerable would be by underground. And even then it's only in comparison, and because they built the whole thing on top of an adventure-prone environment.

[Zaharra]

I agree with what was said by others, and also Waterdeep can also call on numbers beyond their city if something like a seige like the world has never seen were to occur, adventurers, armies, maybe even a few dragons and extra planar entities could be called to defend

And I think The Blackstaff is powerful and well defended, it would be difficult for assassins to kill her and she likely has a clone ready should that unfortunate reality occur

[Vogie]

You've got a pair of mafias (Xans & the Zhents), two levels of police forces (Lords Alliance & Grey Hands), 2 sacred orders (EE & OotG), and an intelligence agency (Harpers). And that's not even mentioning the Guards, Watch, WOMP, and the drow mercenaries hanging out in the harbor.

the number 1 way to take Waterdeep would be by using the Dragonstaff to let Dragons in, past the Dragonward, increasing the efficiency of the naval attack by attacking the city on 2 fronts.