Based on Peri's observations from the rigging, here's a schematic of the main deck, quarter deck, and forecastle:

Dwal

'I dunna think I am the one to ask." Dwal says "Best one of those that have more experience in these things answer ye." 

Gerrard:

Uncharacteristically quiet, Gerrard watches and listens as they approach the spooky boat, taking his cues from Peri.

Kei 

He eyes the looming vessel. Taking what he knows of ships this size he directs Oskar to launch the grappling hooks just shy of the disfigurehead, allowing them to board atop the forecastle. He hopes that this will force any defending crew, whatever that may be, to have to climb from the main deck giving the group a bottleneck to work with.

Oskar nods and throws the hook. Dex check: 18

 He snags a solid spot on his first try and gives a modest smirk.

"Who's goin' first?" he asks. "Won't be me."

Gerrard::

”Right, that’s my cue,” says Gerrard, preparing to climb up.  Then he pauses and asks Peri, “Unless you wish to take the honors, Master Fenwader.”

Peri:

Before the words are fully out of Gerrard's mouth Peri has vaulted from the little boat and clings to the ship's hull like particularly smug crab. He grins, points to his ugly new slippers, and scuttles around to the far side of the Emperor. He creeps silently up the side until he can peek over the rail (Stealth 17). He figures that if there is anyone hiding aboard they will have observed the skiff's approach and seen the grappling hook so they won't be looking for boarders from the other side.

Even in Peri's ugly magical slippers, climbing the ship's hull is not effortless – the vessel is coated with algae, slime, and rot, making it a bit slippery – but it nevertheless does the trick. Peri peers over the top of the forecastle:

It's empty. A short wooden stump is all that remain of the ship’s forward mast. There are stains on the deck, but it is clear of debris.

Gerrard:

More carefully following up the rope once Peri has given the all-clear, Gerrard makes his way to the deck and looks around.  "Seems like we'll have to continue our search belowdecks," he observes.

Gerrard and Peri begin to explore the upper decks, which slope gently down toward the ship’s port side. The forecastle and quarterdeck are empty, and three short wooden stumps mark what remains of the ship’s masts. The double doors leading to cabins fore and aft appear intact, as does the metal grate in the deck that offers access to the lower decks. Aside from the rhythmic creak of the ship’s badly weathered timbers, all seems quiet.

Peri:

It kills Peri to wait for the others to climb aboard when there are so many things that need looking into, but he can already hear Dwal's grumbling scorn if he was to go "pokin' around all higgledy-piggledy with danger about" so he forces himself to stand still near the railing. Well, he makes a real effort anyhow. He does edge over to look down from the foredeck rail to try to see into the hold from the grate, but that's it. But he could go down to the main deck.... No, he'll wait for his slow, grumpy companions here on the foredeck and they'll be sure to admire his self-control. After all, if he's to be a captain someday he should start cultivating some restraint, as Yondalla knows it's not one of his strengths.

Gerrard:

Not the most insightful of fellows, Gerrard is oblivious to Peri’s internal struggle and smiles at the halfling, saying, “So, how does it feel to have your feet on the deck of a ship that is yours for the taking, incipient Captain?  Where should we look first?”

Dwal

Dwal will grasp the rope and mutter to himself "Now I'm a damned monkey". With that utterance, Dwal will attempt to haul himself up the rope.
Athletics check (just in case): 7

Peri:

"Monkeys climb faster'n that..." Peri mutters, seeing Dwal's difficulty ascending. Impatient, he hauls on the rope to help Dwal aboard. "The strongbox is our first priority. Dependin' on size, it'll likely be in either the captain's cabin -- there under the quarterdeck -- or down in the hold. But we're not in a great hurry, so we might as well search slow and steady."

Kei 

His patience runs thin. He too is eager to explore this ship. Not for the same reasons as Peri, but for the plentiful bounty he imagines is sitting in this floating wreck. As Dwal struggles to climb the slick timbers, Kei grasps his cittern and runs a finger down the entire length of one of its strings. Suddenly, Dwal begins to rise effortlessly. "Hang onto the rope Master Primate." He whispers loudly from the deck of the skiff.

As the dwarf gently clears the rail and clambers onto the deck, Kei begins his own accent. 

Athletics 5

Quietly entertained by Dwal's mysterious levitation, Oceanus climbs last, as Oskar pushes off. (He will maintain the skiff about 200 feet off the starboard side of the Emperor, almost halfway between the wreck and the Soul. )

The five of you stand upon the empty forecastle. Peri squints, but can't see anything through the metal grate on the main deck, at least from atop the forecastle - he'd need to get closer.

Gerrard:

"Right, all aboard then.  You said the captain's cabin first, over there under the quarterdeck?"  asks Gerrard of Peri, preparing to head down that way.  Drawing his elegant fencing rapier for a bit of extra light, he starts moving down to the main deck to gain access to the indicated cabin, but he also listens and watches carefully for any sign of hostile inhabitants.

Perception:  14

Gerrard examines the ladder/stairwell down to the main deck. It is worn, stained, and heavily weatherbeaten, but appears solid and intact. Gerrard descends it without incident, and now stands on the main deck. It is quiet, with no sign of any immediate danger. The doors forward and aft are intact and shut. Through the grate set into the deck can be seen a ladder extending down.

Gerrard:

"Well, we really have no idea what we will find here, but I'm ready to open the door once everyone is where they want to be," offers Gerrard, preparing to open the door with his free hand.

Kei 

Now was the time he could repay the nobles actions. Kei would watch over Gerrard's back, just as the noble had his so many times before. "I shall be your rear guard young Sir". Kei shadows Gerrard down to the main deck, staying close but not too close as to hamper the fighters space.