Sly watches all this, mortified.

To everyone else, you see Bilyur become a quipper and zoom towards the drainage point. Fish-Bilyur, now that you’re up close to the crack, you can see that there’s something glimmering gold behind the loose rock. However, since you can’t talk as a fish, you can’t tell anybody about this, nor can you move the rock on your own.

Eggo Lass, much like Sly, watches in horrified fascination. (Um... can you still think? Or are you fully fish now?) she asks telepathically. "Well it only lasts for an hour according to the sign, right?" she says to the others. "Should be interesting to learn what it feels like to be quipper-fied."

[Technically since Polymorph changes your ability scores to the creature, Bilyur now has an Intelligence of 1 💀]

Well, thinks Eggo Lass while contemplating Bilyur's predicament, I suppose there's not much else to do. She turns to the others, "Follow the quipper? At the very least he's got an ear, do fish have ears, to have the ground. And it's up to us to keep him safe while he's in that... form." To Bilyur she adds a singsong, (♪ Just keep swimming. Just keep swimming. ♫)

[[ That said, I think RAW we could theoretically punch him out of polymorph form. Though I'm not sure how Rhino feels about "curative fisticuffs." ]]

[[we could, but I personally think it's much funnier if the characters discover this naturally - it's a fairly high level spell after all]]

"It looks like Bilyur wants to abscond through that drainage point, but I'm not sure how good of an idea it is to let it. What if he gets sucked into it?" Sly is a bit out of her depth, still horrified that one of their members is now a fish.

For now, she wouldn't want to move the rock out of fear of invoking a worse disaster. She looks to the bell construction, trying to find out if there is some way of reversing the transformation [arcana: 11].

Hugh reaches down and taps on the water trying to get Bilyur's attention. "I will ring the bell with the rope in the water, hopefully being close to the rope will allow him to change back. We do have more rooms to explore here."

The fish I'd frantically swimming toward the drainage pipe. 

"I'm not sure that would aid him, Hugh." says Eggo Lass hesitantly, "At best it might create a second quipper on our hands."

She eyes the speeding Bilyur, (FOLLOW THAT FISH! DON'T LET HIM GET OUT OF OUR SIGHTS!) She takes a deep breath and tries to keep pace with Bilyquipper.

(Quippyur)

Sly investigates the bell and finds that it has a transmutation spell on it that will cause it to cast Polymorph on whoever rings it. There doesn't seem to be any way to change Bilyur back using the bell, so you delve into your arcane knowledge for a solution. Although you have not reached such high level spells in your wizardly studies, Polymorph is a fairly well researched and heard of spell, so you know the basics of its effects even if you can't cast it. You know that it will last an hour (this is confirmed true by the plaque), and you also have a faint memory of scholars talking about how Polymorph isn't too effective in combat as sufficient wounds will break the spell, so you get the feeling that if Quippyur were to take enough damage to kill a quipper, he revert back to his original form. However you have no idea whether this damage would transfer to his base form. 

Whilst studying the bell you also confirm it was created by an Orc mage. The name of such a caster entirely escapes you, but you know that they're more commonly seen using Divination spells, so this particular example of their spells may not be am accurate depiction of their talents.

(Splish sploosh)

Sly swims back to the others and informs them of her findings. "Good news; I believe that the spell will expire within one hour. We may also attempt to catch Quippyur and break the transformation via bodily harm."

The wizard is slightly uneasy about the latter option and doesn't offer to do it herself. But she leaves it on the table.

"We could explore further until such time where Bilyur is back to his old self."

Having said this, Sly attempts to peek into the room to the west of the partys position.

Sly dives below the waters surface to look into the room through the door. The room is 15 feet by 40 feet, and looks like it was a large storeroom at some point, but now the multitude of chests, crates and barrels in the room have been pushed to the north-western corner, forming a mountain of storage boxes that break out of the water like a rock on the coast. Sitting atop the pile is a female forest gnome, who seems to be preoccupied paring her nails with a particularly sharp knife. She hasn't spotted you since you're below the water and isn't keeping watch.

I'm a forest gnome - no wait im a quipper. 

Sly swims back up to the others. "There is a forest gnome in the room yonder. She's armed, but I doubt she would assault a group of people. I propose approaching together and asking her about the locale."

The wizard begins taking some crumbs out of her rations and springkling them in the water to lure the quipper to follow them.

Nom nom nom!!!

"Sounds like a plan." says Eggo Lass in response to Sly's idea. She eyes the Bilyur-quipper. I have to wonder... what would happen if we took a small filet? Would it  remain after the polymorph ended? Is that an infinite food hack? Hmmm.... Turning back to Sly she adds, "I could use my telepathy in case she doesn't share a language with us."

The quippyur is following the food trail so closely that if Sly isn't careful her fingers might get bitten. 

The quippyur is following the food trail so closely that if Sly isn't careful her fingers might get bitten.