The back exit of the cavern leads to a tunnel that curves downward. After a few minutes, the air starts getting moister.

Water content in the air is a new pattern! Ana breaks the trance briefly to confirm her guess about what is happening.

"Is there a lake down here or something?"

"I think so. I can't hear it yet but that doesn't mean much."

Can Ana make a sense-tendril long enough to get to the bottom of the tunnel and see what's there if she stops walking and concentrates?

If she sticks to the tunnel, no, though there's a definite increase in moisture between the far end of the tendril and the near end.

It seems likely there is a lake, then! Ana will retract her mage-sense and continue walking.

The tunnel continues to spiral down. After a while, the kobold says something.

Ana turns the mage-sense off.

"Sorry, didn't catch that."

"I can hear the lake."

"There is a lake! Cool!"

Chuckle.

Follow follow follow the dark and windy tunnel down to the lake!

Follow follow. Lake!

The cavern containing it is long and fairly narrow, and the tunnel leads into it at an oblique angle, so that if they kept going they'd be walking alongside the lake rather than into it.

Ana is on board with the plan of not running headlong into the underground lake. She will probe it with her mage-sense. Can she figure out temperature/depth/is there anything alive in it?

That sure is some water. It's very but not completely still, and starts fairly shallow but gets deep quickly; the bottom of the lake is sand with a scattering of pebbles. There doesn't appear to be anything alive in it. Temperature is harder to tell; has she been practicing with that in particular?

Not really, no. But now is a good time to get some in!

Extended examination reveals a gradient that might plausibly be temperature. The highest concentration is near what appears to be the inlet tunnel, where it connects to another body of water, and it changes quite slowly from there through the rest of the lake. It also extends into the air, but dissipates much more quickly there.

That fits with what she remembers from her physics lessons! She can confirm this is temperature by sticking a hand into the water and seeing if what she feels matches up.

...How are they doing on time at this point?

The water of the lake is noticeably warmer than the air.

It's starting to feel like dinnertime; there might be time for a little more flying, though.

"Can you teleport us out and then we can take the scenic route back to Bar? Get back just in time for dinner."

"All right." The kobold's hand bumps hers a second later, and they're teleported back to the mouth of the cave.

Flying time!

Aerial stunts are fuuunnn.

They aaaaare! Swoop! Zoom!

Nyoooooom.

After three circuits of the lake, Ana touches gently down in front of the door back inside.

The kobold hangs in the air for another moment, but then follows her down.

"I never get tired of that," she declares as she's taking the jetpack off.