The adventure

Once they had all ascertained that no-one was severely injured they looked around. Nearby a waterfall fell down a sheer cliff face at the point the beach petered out, leaving just shore and cliff. They set off together in the other direction.
The first sign of life that they found were some large crabs, about half a metre wide. The creatures seemed unconcerned at first, but as the friends approached they turned aggressively and started sidling over the sand towards them. The creatures were more agile than crabs ought to be, and one managed to nip Shu Ting in the leg. Salvador raised the strange contraption he had built and, pointing it at a crab, shot it with a stone.
But the crabs continued to hassle the friends, so Shu Ting hacked them apart with the two swords she'd saved from the wreck, and Quentin crushed the other with the length of metal he still carried. Using the fires from some of the burning wreckage they cooked and ate their first meal. It was a little gritty, but very tasty.
While eating they spotted a building on the other side of the inlet. It seemed to be inaccessible by climbing over the rocks, but the water looked shallow. In fact, they mused, the pool might even have been created by the crash. They waded out to the rocky point and found a clear sandy path leading out of the water, confirming that suspicion. As they climbed they found another group of crabs who once again attacked them. These were larger and stronger, but thankfully had soft, leathery shells.
Margreet and Quentin both tried the incantations they had learned on Grimpak's ship. Quentin's magical webbing sprayed forwards over the crabs, but they seemed to shrug it off and the magic dissipated. Margreet recited over a handful of water and blew the fluid at the crabs. It floated towards them and half the creatures went comatose.
Shu Ting and Karen chopped their way through the crabs, catching sleeping ones off-guard. A crab slashed Margreet badly, but they were soon dead, ready to provide another meal for the friends. The building turned out to be just a wooden gazebo, of the type found in gardens all over Earth. It was a peaceful spot, out on the headland, but not inhabited. They found some potions there and a strange musical intrument, but eventually returned to the beach. If the path came from the beach then there had to be a way off it.

They soon found a door hidden behind a great boulder. It creaked open, revealing a dark tunnel sloping upwards. Inside they saw oil lanterns mounted on the walls, so Quentin took one and lit it from the still hot embers of the crash. Margreet lit another one and the five set off into the tunnel, Karen and Shu Ting leading the way with their swords out. They encountered some very unfriendly living blobs of slime, but three swords and a staff splashed them apart before they could do anyone serious harm. The tunnel eventually rose up into the middle of a chamber with three exits. One was barred by a metal grille, securely bolted in place on the other side. The friends walked up a ramp to another room, where Margreet startled them with a shriek. A splash of corrosive goo had hit the wall next to her. They saw in the corridor beyond another slime.
Quentin tried his other incantation, a spell to immobilise an enemy, but nothing happened. He wondered if this magic lark wasjust an elaborate prank, before recalling the webbing he'd thrown over the crabs. The friends ran over to the slime and splashed it across the floor, but not before it splashed Margreet again.
This second room was a dead end, but it contained the first signs of inhabitation they'd seen. There were three bookshelves and a desk, mostly with financial records for something called 'The Brotherhood of the Ascension'. Margreet found and read a note on the table, written by a man who said that he had sent the brotherhood on a quest to find the 'Destinae Dominus', some sort of holy relic of theirs.
As she read, Quentin also read a book he'd found on the shelves; it was a magical tome of the sort they'd found before, teaching how to make magical light.
They advanced through the underground passages, encountering numerous slimes and some aggressive bats on the way. Salvador's accuracy with his gun got better, but his little stone pellets did little damage. Margreet and Quentin practised their magic; Quentin found that with a little concentration he could make the animals scared, although it backfired a couple of times, leaving the others cowering with fear, rather than their enemies. They picked up a few coins that the slimes carried in them; the slimes seemed unable to digest the hard metal. They found two dungeons, one with a very strange skeleton in it. The skeleton lay on the hard pallet, with two hooves hanging over the edge. The skull was elongated and had two horns protruding from it. As they searched the room, they found a tattered note complaining of the treatment. The prisoner seemed not to have been contented with bread and water. Quentin remarked
"We can see that from how skinny he is now. He didn't need to write it down."
Karen shushed him and read the rest, which mentioned that the weapons were still a threat to Al-Sedexus. They didn't know what it might mean, but it seemed best to keep the note in case they should ever need to ingratiate themselves with hooved, horned beasts. They'd be easy to recognise.
When they had finished exploring there was only one more way to go, and that was through a locked door. Salva had already disarmed a few poison-arrow traps in a couple of chests they'd found, and had no trouble picking the lock. As the door creaked open they heard a powerful clicking sound. It was yet another crab, but a monster, probably weighing as much as a man. The crab's claws were large enough to shear a limb off, and Quentin was glad that he had a weapon to stave it off with.
"I killed all the other crabs" Shu Ting said, "leave this one to me."
"You killed them all?" Quentin was shocked into replying "Didn't I get one?"
"With our help!" Margreet added at the same time.
"Are you sure?" Salva asked, holding his gun at the ready. A little stone pellet seemed unlikely to be of any use.
Shu Ting plunged her little short sword right into a gap in the crab's shell, helped in the effort because the king crab seemed to think that Karen was either a bigger threat or a tastier morsel. It died immediately.
Shu Ting looked smug.

They continued to look around, even finding the drinks cellar, where they poured what remained of the ale in the barrels and drank it. It wasn't good, but they weren't feeling demanding. The ale cellar was over a metal bridge which spanned a river in a deep ravine in the cliffs. It looked shallow, and the fish looked huge, so Quentin jumped in on top of one.
However, the fish was faster than he'd expected and dodged his staff. And more of the large fish swam around a rock top join it. He concentrated on a spell, and the fish fled for a few moments. Soon everyone was wading in the river and they slaughtered the fish in moments. Surprise hadn't worked, but swords did.
The dinner expedition swiftly ended as Karen was swept over by the current. They chased her down, but got caught in the flow as the river reached a waterfall. All five friends slid down the watery slope, panicking for their lives. They landed with a bump on a ledge half-way down the waterfall. They could see the very same bay that they'd just crashed in spread out below them. Shu Ting, never one for dramatic moments, interrupted by exclaiming,
"Look at this!"
"What is it?" Salvador humoured her
She held up a pouch which had been stuck in a crevice in the rock. The fabric was oiled to waterproof it. She looked inside and her face wrinkled.
"Urggh. It's just dust!"
"Let me see." demanded Margreet. She and Quentin scrambled through the water to examine the dust, and they both felt the magic within it.
"We'll keep it." Quentin said, plucking out of Shu Ting's hand and stuffing it into his pocket.
They took their time planning the slide down the fall to the shore, and enjoyed it much more as a consequence, before wearily trudging back up the corridors to the King Crab's room. They slept for the night amongst the barrels there.

Or they thought that they would. They were woken by giant rats, who seemed to find the taste of fresh Margreet quite irresistible. Margreet, ever the discriminating sleeping partner, was not happy with the would-be bed fellows, despite their avidity (or perhaps because of it). The rats had remarkably sharp claws and teeth, and it took a number of flashes and bangs from Margreet's rapidly expanding repertoire of alchemical attempts, and a lot of psychic fear from Quentin to stop them overwhelming the party all at once. But most of all it took a lot of sword slices.
The friends tended their wounds, with magical aid from both Quentin and Margreet, and settled down to rest again.