Shipwrecked in Saltmarsh

((How far away is the Stone from the ship?))

The captain is struck by Kelnan's frigid beam, and while he is mostly uninjured, the burly man in black finds his pants and boots encrusted with a thick coating of ice. 
"Foul pigs!" The captain returns fire with his hand crossbow:
Hand Crossbow Attack (vs. Kelnan): 23 P iercing damage: 8
...as he swings his longsword at Dain with his other hand:
Longsword Attack (vs Dain): 25  Slashing damage: 12

The boy next to him, still staggering from Molo's explosion, stumbles over to the remains of the the tiller. "Cap'n! The tiller!"

The sailor on the forecastle continues to silently fire his crossbow at the reckless dwarf.
Light Crossbow Attack (vs. Dain): 16  Piercing damage: 7

 Kelnan's shimmering shield protects him from the captain's bolt.
The old sailor likewise misses his shot at Dain. 

The captain, annoyed at his crewman's moor marksmanship, snaps at him. "Shape up, ye' dog!"
At the captain's orders, the old crewman gets in an extra shot:
Light Crossbow Attack (vs. Dain): 22  Piercing damage: 7

The second shot at Dain, too, flies wide.

Fianna, Katernin, and Molo may act next.
The Stone is only about 15 feet from the hull of their boat - a possible long jump, albeit risky.

     "That is OUR boat!" Fianna screams out in anger. "céim gruama" she says much quieter and Misty Step 's her way onto The Stone immediately next to the killer trying to steal it.  "Yip off!" she hollers right in there face and attempts to shove them out of the boat.

Shove Strength Check 2 versus their Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use).

((Pretty sure they're going to win this one...))

If Molo can get to him, he’ll run up next to Dain to stab at the captain with a scimitar, while yelling at Fianna. 

“Do you even lift??” Which is magical in its inspiration (can add a d6 to ability check, saving throw, attack roll, damage roll, or AC)

Attack: 20 Damage: 2 

Fianna teleports in a thin cloud of silvery mist to within inches of the staff-wielding killer.
The little boat rocks in the choppy waters, and Fianna's attempt to shove the man is offset by her lack of sea legs.
Contesting Dex check: 6

 Nevertheless the sailor stumbles in his attempt to dodge and almost falls in, but barely succeeds in catching himself.

Meanwhile, Molo manages to prick the captain in his icy legs, educing an angry cuss from him.

Back on the little boat, the arcane sailor disappears into his own cloud of mist and reappears near the boy on the poop deck of the smugglers' ship. He fires a ray of blue light at Fianna:
Spell attack: 12. Cold Damage: 7

The ray misses. Dain and Kelnan may act next.

(Molo is hobbled by his bad foot, of course, and is restricted to 10 feet of normal movement during combat. Fortunately, he had limped up behind Dain during the pause in combat. His ladder-climbing, like his swimming, is unaffected by his foot.)

Fianna, meanwhile, is slowly drifting away from the ship. Looking down, she sees with horror that much of Fossie's head had been dissolved with acid.

Kelnan 

Pleased with the efficacy of his magical defenses, Kelnan grins and draws a ball of acid from the air. "Kanasam!"

Acid Splash against captain and adjacent crew member: DC 13 Dex save to avoid 1 acid damage.

Kelnan lobs a blob of arcane acid at the captain. (The other two crewmen nearby are too far back to be affected.)

The surprisingly nimble captain dodges: Dex Save: 7

 ...and easily sidesteps the splash of magical liquid.

"Boarders! Leave this ship or die now," bellows the burly man.

Dain may act next.

Dain is fully focused on the captain ahead of him.  His eyes narrow and he lets out a huge grunt of effort as he swings the giant maul up and over his head.  With a terrible scream, he brings it vertically straight down at the captain, aiming to squash him into the decking!

Action:  Recklessly Attack the captain, striking to subdue:  Attack: 25 Damage: 24.
Move:   Should the captain be struck down, Dain will move forward to the two other sailors on this deck, trying to engage them both.
Note:  This leaves Dain granting Advantage to any who would attack him before his next turn.

Dain clobbers the captain with a devastating blow to his head. He staggers and looks blank for a moment, but does not fall. 

"Stand down!" he shouts at Dain, slurring slightly, blood dripping down his face.

He recovers enough to take a wild swing at Dain with his longsword, using both hands.
Longsword attack vs. Dain: 16. Slashing damage: 15

The crossbowman on the forecastle takes another shot at Dain as well:
Light Crossbow Attack: 17  Piercing damage: 3

Both attacks strike Dain, the sword leaving a nasty wound on his hip.

Fianna, Katernin, and Molo may act next.

Dain growls further in anger and pain as he is struck twice, by sword and crossbow bolt.  "Fall down, dammit!" he replies to the captain, clearly not prepared to give any quarter in this fight.

(Dain took half damage from both sword and bolt due to Rage and is looking moderately injured now.)

(Dain don’t forget the inspiration can be added to AC) 

Molo attacks the captain alongside Dain with his scimitar

Attack: 10 Damage: 2 

Then shouts at Katernin. “Sock ‘em in the eggsack!” a magically inspiring bit of advice (take a combat inspiration)

((Can I?   If possible and not rewinding time too much Mr Dm, can I add 1d6 (1) to my AC versus the captain's sword attack?  I would need to roll 2 or more to make him miss.

Edit:   Ha ha ha!   Typical.   So, assuming I'm able to add to my AC, I would have used it there and it would have been unhelpful as the captain would still have hit me after me rolling a 1.   Oh well - thanks for the help anyway Molo!)).

     I obviously did not think this through, Fianna thinks to herself as she stomps her foot on the rickety dingy. She quickly thinks better of doing that again!

     Truthfully she expected to battle it out with the other magician, not for them to turn tail and leave her stranded on a boat..,  still, nothing for it but to get back into the fray!

     Fianna does what she can to paddle the boat back to the ship so that she can climb back aboard...

     FinFin too will get back into the midst of things. The pseudodragon will swoop down, dive bomb the captain from behind, and just generally do their best to be a glittering distraction in an attempt to help out .

Molo ineffectively whacks the captain's legs with his scimitar, while Fianna paddles her way back to the side of the ship.

FinFin swoops the captain, attempting to feint and distract and help Dain's next attack (giving him advantage.)

The staff-wielding man steps further back, behind the tiller and the lantern boy, and fires a beam of crackling blue energy at Dain. 
Spell attack: 24. Lightning damage: 6

 A sustained arc of lightning forms between the staff-wielder and Dain; the lightning continues to burn.

Dain and Kelnan may act next.

Dain shrugs off the lightning blast (half damage due to raging as a Totem Warrior) and focuses his attention on the captain.   Somewhere deep inside his unconsciousness, he recognises that the strange little dragon is actually helping him by swooping in to distract his opponent, so he concentrates on timing rather than all-out offence as he usually does.

Action:  Attack (with Advantage due to FinFin, not attacking Recklessly):  Attack: 17 Damage: 13
Note:  Still raging, Dain will move forward if he can finally put this damned captain down.  He is attacking to subdue.

Dain indeed takes the captain down. A second knock to the head with his maul renders him unconscious on the deck. Remaining on deck is the man with the staff, the old guy with the crossbow, and the boy with the lantern.

Kelnan may act next.

"Yeeaargh!" cheers Dain as he finally brings the captain low.  If possible he would like to move up to and engage the man with the staff (using his Move action)?  Failing that he'll try and reach the boy with the lantern.

Dain, who still is connected with a sustained electrical arc with the man with the staff, is able to duck past Molo and run to the stern of the vessel to engage with him.

Kelnan, down on the main deck, can see the man with the crossbow, but not the other two. He'd have to run across the deck and climb the stairs to make visual contact with the staff-wielder or the boy.

It's very dark. The ship rocks a little. A bitter cold wind gusts. The only light is the thin, skewed beam of the boy's mostly-closed lantern and a very tenuous ambient glow from the sky - perhaps from the moon, somewhere behind a wall of low clouds.

Kelnan is up.

Kelnan gives a cheer when the captain falls and shouts as he makes he way to the forecastle for a clear view.

"Anyone else? You disgrace to the profession, you're next!" He carefully levels his rod and fires a crackling Chromatic Orb down the length of the ship at the staff-wielder.

Attack: 18 Lightning Damage: 17