Evi returns to the lower deck and grabs another round of harpoons before making her way back up.  As she does so she'll also call out "I think I found the captain.  Don't think they''ll be much help at this point though." 

Strength: 3

Evi is able to carry another 5 harpoons.

Up next is Tender/Ormidal

Tender picks up another harpoon and throws it at the serpent with all her might. "Go away," she yells at it, her tail lashing behind her angrily. 

Attack: 7 Damage: 8

(wow.)

Orimdal closes his eyes a moment as he refocuses and replenishes some of his magical energy (Bonus Action: using 2 sorcery points to recover 1 spell slot). He then gathers magical energy within his palm, swirling and pulsing through various forms before hurling the mass at the serpent again, "Let's be done with this," he mutters (casting Chaos Bolt). 

Chaos Bolt Attack: 6 Damage: 10 psychic damage

The harpoon streaks past the monster, plunging into the water below. Ormidal's Chaos Bolt ripples past the Serpent, flying off into oblivion.

Up next is Kallista

Kallista releases another arrow towards the serpent, then tries to find a new place to hide on the deck.

Attack: 16 Damage: 8

I don't think anyone is in melee with it, but if there is, sneak attack damage: 2

Stealth: 15

Kallista's arrow hits the Serpent's jaw, causing it agonizing pain. It roars, diving back under the water again. But this time, it quickly makes itself known again by slamming into the bottom of the boat. (Everyone make a DEX save

Damage: 30

The lower decks of the ship creak and groan. The whole ship shudders briefly, and it feels as though it's on the verge of splitting in two.

Dex save: 23

Dex Save: 18

Dex Save: 5

Orimdal Dex Save: 10

Dex save: 10

The hit to the hull does more than just damage the ship. Tender, Kallista, and Ormidal manage to stay standing, considering the circumstances. Fletcher falls backwards onto his bottom (taking 3 bludgeoning damage as he lands). Evi completely loses her footing, and the hit throws her through the wall of the lower deck (taking 1 bludgeoning as you fly through the splintering wood). She continues plummeting towards the salty sea, where the Serpent lurks...

Up next is Fletcher

 getting back up to his feet (Half movement), he sees that Evi has fallen. Without hesitation he jumps through the hole in the upper deck, aiming for the floor of the lower deck. (Acrobatics 25) Then he will try to pull Evi out of the water 17

Fletcher is able to get to Evi. Looking down into the water, you see only the two glowing eyes of the Serpent, about 60 feet below.

Up next is Evi

Evi, panicking at suddenly being thrown into the water, will attempt to swim as furiously as possible in the direction she believes is up & towards the ship.

Athletics: 16

Evi is able to breach the surface of the water, seeing the ship about 15 feet away.

Up next is Tender/Ormidal

Tender, wide-eyed and slightly terrified, readies another dart to throw in case the serpent reappears. "Fletcher! Evi! Are you down there?"

Fletcher is paralyzed with fear, staring into the serpent's eyes.

Orimdal ensures the ship is holding it's course, holding the wheel steady in one hand and holding a fire bolt in his other hand as fire whirls around his hand ready for the creature to emerge again.