Cannons in the Mist

A battle at sea between a pirate ship and a ship of the Dwendallian Empire. The party is on the pirate ship. They have joined the pirates' cause and are focused on ships returning from Eiselcross, possibly carrying artifacts looted from the ruins of Aeor. Both ships have cannon / ballista. Assume the Empire ship is bigger and more heavily armed. But the pirate ship is faster and more manuverable.

Battle phases:

1. Locating and intercepting the prize. The players will have to come up with a strategy here. It may involve epionage - getting a look at the opposing captain's charts - or stowing aboard a spy to report position. They may have access to arial scouts, and follow the ship out of Balenpost. Be sure to "Yes, and..." the players' schemes.
2. Engaging the prize ship. The pirate ship has advantage of speed and manuverability. It can tack closer to the wind, and make tighter turns. The captain should explain these advantages to the PCs, and let them make the tacticle decisions. PCs can make skill checks to aid the crew, encourage imaginative use of magic. Run it in increments of 30 minutes per turn - ships can: turn - turn; attack - turn; attack - attack. Correcting course to aviod collision is a thing. Also wind direction is a factor.
3. Boarding and defeating the imperial crew.Run as standard combat, using battlemap. Climbing the rigging gives bonus to ranged attacks. Provide plenty of ropes to swing on, flammable items near cannons, stairways to bottleneck or fall into. Falling overboard hazards.

Environmental hazards:

• sea fog - limited visibility
• nearby coastline/islands - running ashore
• disturbing monsters in the deep - may come out to play
• ocean temps: to cold to survive long in water

Theme (high fantasy) reinforcements: target absolutly has one or two mages of the CA aboard. At least a glimpse of a sea monster should happen. Possibly ghost ships within fog? This can provide urgency to leave prize ship quickly after battle.
Part of adventure: Escape from Balenpost.
NPC's Pirate Crew: Captain, 1st mate, Bosun, Quartermaster, Surgeon, Cook, misc deckhands. Each officer is shadowed a PC. sailors are considered "minions". At any given time at least 12 sailors are occupied with sailing duties, or the ship looses speed.
Dwendallian crew: For chase and interception, not important. During boarding assume same 6 officers, 30 sailors and 2 mages - specialized in elemental magic. Be sure to determine commitment level of officers and mages. Some of them should be named PCs. Is this a prestige command or a backwater? Is the captain proud of his ship, or does he resent this assignment? Is the first mate loyal, or can he be flipped? Will the sailors fight the pirates, or join them?

meta references:
tacking
game mechanics reference:
UNEARTHED ARCANA: Of Ships and the Sea

Map: Balenpost to Ice Haven, costline and islands - here
Sea battlemap here
Ship maps here

Links to NPC stat blocks here