(I'll roll for Skulk for the time being.)

Skulk hurls a second harpoon into the massive whale. Attack: 11 Damage: 8

The whale bellows and submerges under the water. You can just make out its dark shadow under the waves, swimming northward.

"Don't lose that whale!" Luc-Pierre shouts, giving Ox a hand up onto the boat as a shark lunges for his legs. Attack: 14 Damage: 8

He takes up an oar, his eyes wild, and begins rowing frantically after the behemoth. Whisper immediately follows suit.

The shark misses me. 

I duck underneath the water, and fire my crossbow at the whale.

Attack: 16 Damage: 9 + 3 radiant damage

If the attack has disadvantage, this is the next roll (Would it be disadvantage underwater if the storm isn't underwater?):

21

Once I hit/miss with my crossbow, I pull my head up above the water and pull myself on the boat so I'm not left behind. That'll give the shark an opportunity attack. 

Dane frantically keeps rowing as well.

Nylia picks up her parents and rows after the whale.

Ahead of you looms a wall of grey mist. Neither the whale nor the captain change their course, and you are soon swallowed by the vapor.

So dense is the mist that you cannot even see the water below you or your fellow rowers. It presses in on all sides, smothering your thoughts and movements. Time ceases to exist in this silent world.

You come shudderingly back to reality in an explosion of shattering wood. You have emerged from the mists to find yourselves run aground on a dark beach of pebbles and gravel. A gaping cave looms before you.

Several figures hang over the dark maw of the cave, suspended by their necks with coarse rope. Closer inspection reveals that they are the remains of seamen, at least three months old.

Nylia looks up at the cave, then to the crew of the boat, making sure that they're all still alive. Once she confirms that they are, she puts her gear on and makes sure her shield and sword are at the ready. She looks for any sign that the island (assuming an island) has any sign of inhabitants other than the cave. (Survival: 18)

"Shit. How far are we from the boat? Do any of us have familiars we could send back? What about stuff to repair the rowboat?"

I climb out of the row boat, making my way towards the cave with my still glowing crossbow. I observe the corpses for a moment, just making a note of their races, and then move into the cave.

Answering Nylia, "Nope, I have no pets. Let's check out what's in here."

Dane is simultaneously thrilled and devastated to suddenly be off the water.  This sudden change of situation takes some time to get used to, at which point he looks around and observes the corpses.  He casts Light onto the front of his shield.  He then sees Ox.  

"You look like crap.  Here."  Dane casts Cure Wounds, healing Ox for 5.  It burns like a brand, and there's a mild smell of burnt flesh.  However, after that, the pain from your wounds eases.

Luc-Pierre curses and dusts himself off while Whisper examines the damage done to the rowboat. 

"She's still seaworthy, captain." Whisper chokes out painfully. "Give me a couple hours and I'll have her fixed up with emergency patch."

"No!" I tell Dane. "We can't take just a rowboat out to sea! What are you trying to do? Get as all killed? We'll need that for firewood if we want to survive on this island."

"Thanks for the healing, let's check out the cave."

(Just for clarification, I wasn't trying to take the rowboat anywhere. I believe that's the captain and whisper. )

(I know, my character still holds a grudge, and will keep trying to make you that bad guy for this. Nothing personal, just a character thing.)

(Seems fair.)

(Also, a clarification. My light crossbow will remain glowing while I hold it, until I rest. It continues glowing forever.)

It is with a grim sense of foreboding that you approach the cavern, ducking under the corpses which sway in the wind. The rain has finally stopped, but the dead silence is almost more terrible than the thunder and lightning.

The inside of the cave is pitch black. Water drips from the ceiling, forming in puddles at your feet. A natural tunnel leads deeper into the cavern.

Characters without darkvision will need torches or some other source of light to see anything. If you want to proceed, I'll need a marching order and descriptions of what your characters are doing.

Nylia cautiously makes her way to the front, shield up and sword poking at the ground in front of her, feeling for traps (and looking ahead with darkvision).

Perception: 16

Looking around with his lighted shield, Dane sees the path in the darkness.  Holding his shield ahead of him (thus shedding light ahead of him), Dane starts walking down the path.

Edit: I'll take spot two, behind Nylia.  I'll also look out for traps. Perception : 16

My crossbow sheds bright light in a radius of 20 feet

I will lead. I also have darkvision.

 (Have we reached out to Skulk?)