Ben:

Casting around and looking for a boat or raft of some kind, Ben also looks back with concern at Matilda and the Owlbear, magically barred from this island.

Perception for a boat:  21

Getting desperate Matilda scrapes off some tree sap and sticks small twigs to her and the owlbears foreheads...

Ben examines the lake and its shores - there are no boats here, nor any other signs of civilization.

Matilda finds to her surprise that while the sap doesn't adhere, simply holding a stick to her head allows her to approach the lake. As to the owlbear, she finds a stick "horn" is relatively easy to fit into position in the stiff feathers on its head. Silly, but effective.

" This enchantment is not very smart.....", Matilda muttered.

" How do we get across? Is it shallow enough to wade through?"

Horatio calls up to Ben. "We could fell some trees and make a quick raft. It'd take two, maybe three hours."

Ben:

Getting out of the costume, Ben starts taking off his gaudy armor and strips down to his plain stonemason's clothes.  Folding it up and stacking up his equipment atop it, he keeps only his clothing, his amulet, the tiny magic sword (secured in his boot like a dagger), and his pouch.  "I will check," he responds.  Holding the pouch above the water as he gets in, he moves a bit into the water to test its depth, stopping if he has to start treading water.

Athletics to move about in the water if needed:  18

Titaani looks at the water with deep dislike. “I like the boat idea better.”

Ben takes a dip. The bottom of the lake, initially shallow, quickly drops off. The water is quite deep fifteen feet from shore. But the water is calm and refreshing. In fact, it's rather invigorating. Ben can feel the fatigue leaving his body. The owlbear dives in recklessly, diving and splashing with obvious pleasure.

"So... we won't get lost swimming the lake without the costumes? I don't want to discover this is something like in the woods where you lose your way if you're not dressed up for it... At least in the woods you can turn around, out there we would drown."

Matilda follows the owlbear with a giggle..

Ben:

Uncharacteristically carefree, Ben calls back, "Come on in, the water's fine!" as he begins to swim towards the island.  He keeps his pouch above water as he does so, hoping to keep the fire-making materials dry.

Ben, shorn of his costume and armor, swims across the 250 feet of fresh, still water without issue. In fact, he feels rather invigorated by his swim. The steep, rocky islet is 30 feet wide and 40 feet long. Perched atop the islet’s highest point, 30 feet above the surface of the water, is an iron bowl filled with coals.

Ben:

Setting his pouch on a dry spot near the shore, Ben gets back in the water and swims around, enjoying the refreshing sensation and trying to be relatively close by to the others if they struggle with the swimming.

Matilda points the owlbear towards the island and hangs on...

Horatio shrugs, then strips down his non-essentials into his backpack. He throws together several large branches from nearby trees and lashes them with twine. Once done, he swims out towards the island, his little raft holding his bag (mostly) dry. 

Horatio, Matilda, and her new friend all successfully swim to the islet in the center of the lake, joining Ben.

The islet is lush and green, studded with a few sizable boulders and a small grove of very healthy trees. Seen from the islet, the distant shore from which you swam is now partially cloaked by a hazy mist.

(Happy New Years everyone!)

Titaani nervously squints at the mist surrounding the island. 

“I mean, someone has to guard the rear, right?” She says to Tiny. “Something could come after them from the shore!”

Tiny gives her an unimpressed look.

”Fine! I’ll go! You stay here,” Titaani snaps, grabbing twigs and twine and lashing them together like she had seen Horatio do. “Bite any unfriendly people who come along, ok?”

At Tiny’s nod, Titaani hesitantly begins to paddle towards the island.

The four adventurers all manage to swim through the invigorating fresh water to the small rocky islet, while Tiny remains behind to watch the shore. You're able to keep most of your important belongings relatively dry, and those things that get wet dry quickly in the effervescent fey climate here. 

At the top of the small island hillock you can see an ancient, weathered iron bowl, heaped with fresh coals. The kids had told you that summoning the unicorn, "Lamorna", could be accomplished by lighting a fire in that bowl.

A small school of lazy fish drifts visibly near the surface, as small birds dart a few feet above, careening from one end of the lake to the other in the delicate mist.

Ben:

Once everyone who is coming arrives, Ben picks back up his pouch and moves to the top of the island where the coals are.  Taking out his flint and steel, he starts lighting the coals…except…nothing happens.  This same curse has followed him to the Feywild, and he can produce nary a spark with even the most vigorous strike.  He sighs in frustration and sits down heavily on a nearby rock.

Horatio will help Ben light the fire.