"Can you hear me?" calls Bella. Sherlock can hear tentative Bella-footsteps.
She follows Bella as best she can.
Sherlock's path - pitch dark with the loss of Bella's glowy thing, unless she chooses to set something on fire - divides, as best she can tell by listening to echoes and groping around, into stairs up and to the left, stairs down and to the right, and a scrunchy twisty passage that goes forward and slightly angled downwards.
She can't hear Bella walking anymore after she's gotten about ten feet in.
The twisty passage's back end apparently now divides into three equally twisty passages (left, right, and forward-and-down) in that direction.
She can hear Bella again, if that's Bella running and making breathy fearful noises somewhere off to the left.
Sherlock quickly becomes very good at not touching the glowing moss. She also keeps following the sound of Bella's voice.
There's a wall behind her again.
There may be something moving in the water, deep under the surface.
She holds a hand out to one side and slightly behind her, and ignites her gauntlet.
Well, if there was something moving in the water, it's not making the water ripple anymore, although it's possible that from her vantage point there are parts of the pool she can't see, cut under the tunnel she's standing in.
Under this completely still water swims a dark shape.
Also, it does not appear to be limited to travel through the water. It rises, surface yet unrippling, and swims through the air, jaws wide; it looks like a cross between a shark, a weasel, and a sea anemone, and it's six times Sherlock's size.
Till the moment when it bites her in the legs. Then it's there.
The creature steams, then smokes, then burns.
When it is very thoroughly charred, it at last stops trying to eat her, and falls into the water, diminished but no longer insubstantial and therefore splashy.
There is no exit but the water; therefore, logically, the water is the exit.
She doesn't jump so much as stumble gracefully off the ledge.
She fetches up on a smooth, gently sloped shore in a cavern that is completely white, made of something that looks sort of like alabaster, and populated with rather a lot of frogs of various shapes, sizes, and colors.
It is down these stairs that Bella shortly comes racing, terrified and breathing hard and chased by a flock of toothy batlike creatures. She doesn't appear injured, but considering her preparations that doesn't mean much, especially since there's a few splotches of blood on her outfit and a few new scratches in her armor.
She spots Sherlock and runs in her direction, pursued by bat-things. "Shr-" She chokes and coughs up a blue medium-sized frog, which she catches, bewildered, as she skids to a halt before entering the water.
Bella drops her frog, pulls a handful of something powdery and green out of her sleeve, and throws it at the bat things. She hits four of the flock, and those retreat into miscellaneous exits, shrieking, but the others get at her and start nibbling at bits of Bella that aren't covered by armor. Bella does her best to swat them away - none of them is bigger than size of her outstretched hand - but there's about forty. She eventually gives up on doing anything about their insistence on nibbling on her and attempts to help Sherlock out of the water, upon which exit the bat things begin to nibble Sherlock too.