Fork commands the Scout crew; with a 20 on insight all 4 surviving scouts get advantage on their attacks.
Fork's drake attacks and hits for 5 damage
Scouts move into position on the stern and make 4 morningstar attacks with advantage (1 crit, 3 misses) and 4 bite attacks with advantage (2 crits, 3 hits, 1 miss) for 36 damage
The Broad Fin is bloodied at this point.
Tegu moves into position amidships and goes into a rage, attacking recklessly. Hits with her melee attack for 14 damage and her hungry jaws attacks for 8.
Legendary tail attack from the Broad Fin on the White Cliff -- 7 damage to the mount and 14 to the ship; however 14 damage fails under the damage threshold!
Servius commands the gunner crew; with a 25 on arcana all 5 gunners get advantage on their attacks.
Gunners make 15 Fire Ray attacks with advantage, with 6 hits and 1 crit for 32 damage.
Sustained damage to the head and middle coil cause the sea monster to reposition, losing the grapple entirely.
Broad Fin:
HP lost: 107 head / 0 first loop / 43 second loop / 0 third loop
AC: 17 + 2 for partial cover (doesn't apply to White Cliff)
Crew: 5 gunner, 4 scouts, 5 carpenters, 5 medics
White Cliff:
Mount HP: 134 / 170
Ship: 71 / 130 (damage threshold 15)
22 - Enemy Serpent
19 - Siduri
18 - Cauda
17 -Fork
16 - Ttharg
15 - Tegu / 4 Scouts / 5 Gunners
10 - Nibum
8 - Kabett
4 - Servius
3 - Capt. Magyar / Cocytus / 5 Carpenters / 5 Medics / White Cliff
SPECIAL ACTIONS:
Spells can be cast on the White Cliff's mount without having to touch the beast's skin; there's a reason it's called a living ship.
Kabett can use his action to command the White Cliff's mount to fight; otherwise Cauda will command it (losing her turn). Here's a statblock:
https://www.dndbeyond.com/monsters/2...nt-sea-serpent
(bite or breath attack ONLY -- the ship is in the way of the other attacks)
The rest of you can each use your action to direct the actions up to 5 members of the crew for various purposes.
Servius can direct a salvo from the gunnery crew, giving some of them advantage on their attacks. Otherwise, the First Mate will command them (losing his turn). The number of crew aided is determined by an Arcana check.
https://www.dndbeyond.com/monsters/2...arlock-of-imix
Fork can direct a melee attack from those trained as scouts, giving some of them advantage on their attacks. Otherwise, Tegu will command them (losing her turn). The number of crew aided is determined by an Insight check.
https://www.dndbeyond.com/monsters/3...lk-scaleshield
Nobim can direct a repair action from those trained as carpenters, who will each attempt 2 repairs. Otherwise, no repairs will be attempted.
(+4 to the check, 1d6+2 repair on a success, DC increases as the ship takes damage)
Ttharg can direct a triage action from those trained as medics, which will stabilize injured/unconscious crew and get them out of danger. Otherwise, crew will be left where they fall.
The Captain can take a morale action, giving inspiration to up to three crew members, in place of her action.