Dwal ducks behind Kei and the mast to get close enough to Peri and Gerrard to help. (The spell has a 5' range.)

CON Saves:
 9
 3

Dwal's divine word weakens both swarms somewhat. Gerrard manages to mash many  - but not quite all - of Peri's little attackers with his rapier. These little pests are persistent and difficult to eradicate. And they have effective little pincers. 

Bjorn tries again to peck more off of Gerrard:
Bite Attack: 24 Piercing damage: 5

He does better this time, gobbling up a maw-full. (Crit damage: 1) 

Oceanus tries to break free of the web he is trapped in:
DC11 Strength check: 22

Impressively strong for his size, the aquatic elf easily tears free of the webs. (The area, however, is still covered in the sticky strands.)

Peri is up! He and Gerrard are still infested with the little horrors, although the swarms are reduced in size and bite.

Peri:

Peri's martial arts are proving ineffectual in ridding himself of pests. Maybe Gerrard is onto something, he thinks, and starts trying to clear the spiders off the nobleman. (22 for 8 + 18 for 4) It enters his mind how this must look to the dwarves aboard the Winter, who likely can't see any spiders and instead just see two of their erstwhile passengers flailing away at one another in the most pathetic duel ever witnessed. The thought makes him laugh, and now he thinks they must be watching a halfling cackling madly as he tries in vain to skewer one of his friends. They'll be thinkin' it's some powerful mind control, like the succubus in the citadel, and really it's these damned bugs! he thinks, and is now wheezing so hard with laughter that the tears are ruining his aim and Gerrard might actually be in danger. Yondalla help me, if we don't kill these critters soon we might all die laughing!

It takes all he can give, but Peri just manages to clear Gerrard of spiders. The only remaining swarm, reduced in numbers but still biting, is on Peri.

The insectoid retreats further from the web-filled doorway and out of sight, somewhere in the debris on the starboard side.

Kei may act next. 🕷🕷🕷🕷🕷🕷🕷🕷🕷🕷🕷🕷🕷

Kei 

Breathe. The insect having left, for now, Kei makes himself take a second. Turning to Peri - "I assume we're going after that thing." More a statement than a question he calls on Mask again to try and finish off the bugs assaulting the halfling.

Word of Radiance 11 damage. Con save 13

Peri's little horde tries to resist Kei's holy utterings: CON Save: 12

 But they cannot. The swarms of spiders are finally exterminated. 

There are no enemies in sight right now. The two larger attackers have retreated into the debris-choked room and are no longer visible (although you know roughly where they are hiding.) The door is clogged with fresh, sticky webs, as is the space in front of it and behind it, and the space around Oceanus.

Dwal and Gerrard may act next.

Gerrard:

Dropping the points of his weapons onto the deck so the stick up like quivering maypoles, Gerrard quickly draws multiple throwing daggers and hurls them through the doorway at the spider he saw moments before.

(Rolling with disadvantage due to likely concealment and some webs in the way...is that fair?)

Throwing dagger attack:  Attack: 19 Damage: 5

Throwing dagger attack:  Attack: 11 Damage: 7

Throwing dagger attack:  Attack: 9 Damage: 5

Based on the buzz and squeak and commotion upon impact, Gerrard reckons the first of his flying missiles must have hit its mark. From outside the door it's impossible to see much - you have no idea if the spider is alive or dead, advancing or fleeing.

Dwal may act.

Dwal

Dwal will pull out a torch. He will light it using Prestidigitation then use Mage Hand to float the torch into the room while remaining outside. 
If the light from the torch is not sufficient Dwal will use Control Flames to cause the fire to burn brighter to allow more visibility. 

Dwal edges a little closer and lights up the cabin. His extra cantrip illuminates the garbage and debris with intense brilliance — the skulls on spikes, the altar, the broken furniture, smashed crates, dried palm fronds, a couple of books, and a badly wounded giant spider cowering under a heap of trash - still living, but barely. The bipedal insect is not visible, at least from Dwal's vantage point.

Combat is paused for the moment. (I will reroll initiative if it begins again.)

The cabin and deck remain still, the tiny spiders finally eradicated. Everyone is free to act. 

Gerrard:

Now that he can see the spider again, Gerrard starts reaching for more of his throwing knives (but he just went, so let's allow others to take actions first if they desire.  Gerrard has no good way to clear the webbing himself).

Peri:

With the immediate danger gone and the two remaining beasts showing no sign they want to come out into the daylight, Peri spends a few seconds shaking the dead spiders from his clothes, disgusted by the number that fall out from beneath his shirt. When he is more or less vermin-free he moves to see into the cabin illuminated by Dwal's torch. He sees the torch light reflected from the spider's compound eyes where it remains motionless, as though the party won't be able to see it if it doesn't move. Fearsome predator, but none too bright, he thinks, amused at the unintentional pun. "Mr. Fiercehammer, get that torch out of that cabin," he barks, channeling the voice of the bosun on his first ship, coincidentally another surly dwarf to whose orders even the rowdiest of sailors responded with alacrity. "Between the webbing, the trash, and all the busted up furniture the room's like an oven waitin' to be lit, and we don't want to burn this hulk til we've got the strongbox." Keeping an eye on the doorway, he will ready an eldritch blast should either the spider or the bugman poke their heads out.

Dwal

'Ain't no fire I can't control lad." Dwal says with assurance. "I ain't gonna burn yer pretty boat. If'n something gets a flaming I'll use me power to put it out a'fore it does damage."
With that Dwal will keep an eye out for the flames catching anything on fire. If even a spark pops off he will extinguish it. 
Dwal will maintain his control over the torch. If no one does anything else Dwal will pull the torch out and extinguish the flames. 

Dwal manages to keep his flames under control, and the wood and debris has an inherent dampness to it that makes accidental ignition unlikely anyway.

The spider remains motionless, hiding under a pile of trash in the far corner of the cabin.

Oceanus reports to Gerrard and Kei in Elvish that he saw the bipedal insectoid for a moment, hiding near the stairwell down on the starboard side of the cabin. (Nature check: 20 )

He knows little of the nature of this creature, but Oceanus recognizes it well enough to know its name: an "ettercap". He has heard of wild, gloomy, forested islands overrun with them.

Gerrard:

With his knives out and now able to see the spider in the torchlight, Gerrard flings another brace of blades at the spider before Dwal puts out the flame.

Throwing Knife:  Attack: 26 Damage: 6

Throwing Knife:  Attack: 25 Damage: 5

Throwing Knife:  Attack: 11 Damage: 7

Gerrard's flying knives soon puts a quick end to the cowering creature.

A tangle of sticky webs continues to block your path (to advance, search, or retrieve one's throwing knives.)

The ettercap is nowhere to be seen.

Gerrard:

"So, is everyone alright?  Do we have a way to clear these webs without setting fire to the ship?  I suppose we could try another way in, but I only have a limited supply of my throwing knives," mentions Gerrard, looking around to see how the rest of them are faring.

Peri:

Peri ponders the webbed-over doorway. An idea occurs to him and he tells the others, "Keep an eye on the door; I'll be right back." He dashes up to the forecastle and retrieves the grappling hook the others used to board the ship. He hurries back to the main deck. "Get yourselves set up around the doorway -- not too close now, no need for anyone to get bit when we've got the critter cornered. I'll throw the hook through the door and dredge out the webbing. With any luck the thing'll go after the hook and we'll be able to shoot it full of holes from out here." Peri positions himself just to port of the mast stump and stabs his spear into the deck at his feet, ready to hand if the beast charges. Since his hands will be occupied with the rope he offers the crossbow to anyone who would like to use it. Once everyone is in position, he lobs the hook through the web, careful not to go far into the room so he doesn't snag it on anything, and heaves. (Raw roll if it's needed: 20. If it's a Strength check his modifier is -1)

Gerrard:

Gerrard will pluck up his blades from the deck and stand to the side of the door, ready to stab anything hostile that emerges and waits for Peri to execute his plan.

Peri tosses the heavy grappling hook through the tangled web and onto the damp floor within.  Sticky webs clot and tear as he pulls it out.

He tries it again, and then a third time. It does a pretty good job tearing a sizable hole through the web, but it doesn't trigger any attacks from within. It does, however, make the doorway passable once again (at the expense of making a bit of a sticky mess out of the grappling hook.) On his last attempt he manages to pull a broken stool out as well. 

Gerrard:

With a smile, Gerrard says, “Ho there, Fisherman Fenwader, I think you have hooked a live one, or maybe just its excrement!”

Levity aside, he adds, “Right, are we ready to proceed?  Oceanus, where did you last see the...Ettercap, was it?”