Mrrrglbgllrr. Merrin misses when her problems only required her to do LOTS OF MATH and not also SOCIAL DECEPTION.

....Okay, perhaps Laeirthe is now going to have to take a turn being contrarian in the POSITIVE direction, to point out that Merrin now has a much better set of problems! Even if altered-or-alternate-world-version-Estha is terrible, it seems he's not-impossible to cooperate with, and she has access to economicmagic for food and climate control which basically just solves her most-likely-to-be-lethal problems, and also MAGIC EXISTS, and she might have a way off the planet, and - wasn't she whining just a few planetary months ago about how everything felt meaningless when none of her decisions affected anyone but herself? Doesn't she prefer the scenario where her decisions might have important consequences? 

Wow Laeirthe is really bad at the 'positive' thing and also has a really bad model of her, somehow, Merrin actively doesn't want to be in a position where anything she does as an individual has important consequences, that's a matter for Civilization, not a medtech who isn't very smart

Merrin can recognize that her feelings about the matter are...somewhat more complicated than that. And also that there are a lot of things more important than her feelings. 

...Internal conversations go fast, but it's still going to get weird and awkward if she goes thoughtful and quiet for any longer. 

"- I would say 'understood' but I'm not actually sure I follow all of your logic," she says. "Which - isn't surprising, since you're not explaining the cognitohazard parts, so I don't have the context you're reasoning from. I - acknowledge your decision." 

<actual reaction>Well GEE THANKS for your generous acknowledgement, miss wayward subordinate.</actual reaction>

<spoken reaction>"Yes.  I do apologize both for its inconvenience, and for necessarily arrogating that decision to myself if it's to be made that way at all."</spoken reaction>

It's less humiliating to say in Utopian, at least.

And eventually Merrin's suit navigation informs her that they have now walked 9.6 km, which was her conservative guess at the conversion from six "miles". Here seems like a fine place to cast the sourceless-geology-knowledge spell?

She's the one with the Dark Tapestry inverted-magic precise navigation equipment.

[Lay of the Land].  Focusing particularly on knowledge of rivers and the places where water can go, including underground to realistically swimmable depths, if the spell lets him request maps of that part.  He is explicitly not interested in just the above-ground parts of the geography.  Esta wants to know the lay of places he might swim, not just places he might walk; but also he doesn't want his brain-crushed by a full 6-mile sphere of geography...

"Your idea for riding the returning tide was an excellent one.  I would very likely have picked up the [Bag of Holding], I now think, if its location were confined to the river we are walking."

"The [Outer God] has correspondingly sent us to a place that is very thoroughly honeycombed with underground lakes and rivers.  And while we should try things the easy way first, I will be surprised if the [Bag of Holding] is not now in one of those instead."

Maybe they would have been better off just not looking for the bag until the Outer God's game had reached a plausible conclusion.

Just commit to not using the Bag's contents if you find them, idiot, and then it may simply be lying near the river as you search the first time.

If Esta naturally thought that way without Rugatonn having ever instructed him on the topic in her own person, he would already be an 8th-circle and her designated successor.

"Oh. ...That makes sense, this is -" The language-sharing did not provide Merrin with the kind of highly precise geological vocabulary that she has access to when speaking Baseline. "- Terrain made of rock that dissolves in water under the right conditions, it tends to form all sorts of underground rivers." 

They might as well keep walking. It would be neat if they can reach the end of the intertidal zone before their safe river-riding window closes, to be sure the Bag can't be any further upstream than that. 

"We might have time on the way back to stop at particularly deep caves," she says. "...I have a mapping -" this language does not even slightly give her a word for 'software', "- I have a thing to draw maps in my armor. It's pretty annoying to do it while I'm trying to walk but I can make a start, if you tell me about caves as we pass them. ...Do you have any other spells that would be helpful for cave exploration? I would be - reasonably safe in my armor," as in, NOT SAFE ENOUGH that Exception Handling would give her this assignment without a lot more support than she has here, but, you know, relatively, "but you don't have the ability to give me the magic-detecting spell..." 

"Not this [day], no.  My priority for the next [day] is to add [Word of Recall] to our loadout.  [Imbue With Spell Ability] would be a reasonable candidate for the [day] after.  And we can maybe eventually work it around to [Air Walk], [Water Breathing], and [Freedom of Movement]."

It does remind him that he might as well cast Heal on himself, this being their probable halfway point.  He has very likely become fatigued by now, yes.

Heal.

Does that by any chance cure Esta's insanity or restore his true memories?

It is, alas, not quite that kind of insanity.

"Well, that didn't restore my own true memories, or any such easy out."

"I do believe I was suffering several forms of affliction beyond simple fatigue.  Some of that may be down to encountering an [Outer God], but other afflictions might conceivably be from poisonous air before I cast the [Planetary Adaptation] on myself... it might be worth repeating the [Heal] on you next [day], if I receive it again, to see if it makes a further difference."

"...I didn't think you were exposed to the -" really, no vocabulary for radioactivity, this language-sharing spell is enraging, "- the cave with the poisonous air too badly, it definitely wasn't enough to be much risk to me rescuing you, but it might've been enough to affect you a bit, yeah."

Merrin does not feel like she's particularly going to need the [Heal again] unless she has a Stupid Accident, but she's not going to say no, if he's offering. It'll definitely make her less cranky about doing intense-physical-exertion exploration missions on two successive wakeful-periods plus all the sleep schedule shenanigans they're going to need to pull if they want to make the best of the optimal-tidal-windows for hunting in caves as fast as possible. 

If Estha is back to full health, then Merrin will have to work somewhat harder not to be the one slowing them down. She's using the bare-minimum power armor assist she can manage with, because she does need the battery to last almost 24 hours and, even if she doesn't need the suit climate-control at all right now, the suit itself still has to keep its internal electronics from overheating. And she's carrying a decent weight of total supplies, even if it's efficiently packaged in the harness webbing on her back – she's got carefully rolled sailweed leaves and enough of her compact-spool-bundles of dried strapwrack to make a minimalist boat, since she's not entirely sure there'll be any to harvest almost 20 km upstream of her normal location the deflated bundle of Estha's stupid flotation suit in case the boat plan doesn't work, and spare oxygen just in case, and some food from her backup dath ilan rations in case there's a problem with the food-production spell, and minimal first aid supplies in case Estha ends up too unconscious to cast healing spells right away, and minimal supplies for emergency shelter in case Estha ends up unconscious and can't get new spells until he wakes up and their climate-control ones run out... 

She's not actually very worried about this being a disaster! It would be a stupid idea to do it if she was worried about that! She's just, you know, trained by Exception Handling. 

They walk. And walk some more. 

They can make much better time when they're both walking under their own power and neither of them is at risk of heatstroke. 

It's still going to take, like, twelve hours to travel 19.2 straight-line km upstream – it's several more kilometers of walking than that, the riverbed is not perfectly straight. 

Merrin is THOROUGHLY bored of rocks. 

She asks Estha to tell her whenever they're passing a cave and describe his sense of its general direction, how deep it goes, whether it slopes up or down, whether it branches and at what angle, etc. The voice-activated visual mapping tools on her suit are being buggy right now – she probably needs to replace a wire, though if she's lucky it just needs proper cleaning or it's a temporary heat-related malfunction – but she can make some use the stupid touch-sketchpad function on her wrist console screen without slowing them down or tripping over her own feet, and at the very least she can keep a full audio recording to review later against the location data. 

When she's not noting down cave features, she'll...ramble, apparently, about dath ilan. Since Estha wanted to hear about it in case it jogged memories loose or something. And because she's really bored. 

She's mostly inclined to ramble about the medical system, and what she knows of how Exception Handling is run, but a lot of stuff will come up incidentally – the secrecy oaths, some snippets about the structure and selection of dath ilan's Governance, some bits and pieces about her early schooling before she started working as a medtech. 

It's hot out. It's so hot out. Not that this is inconveniencing either of them in any way, except for reducing the efficiency of some of Merrin's power armor electronic functions, but by 34:00, a few hours after solar noon and ten hours after they set out, the temperature peaks at just above 50° C.

Still well within what Endure Elements can handle, but one assumes that real summer on this planet will be even hotter than that. 

...They're only 18.3 kilometers upstream of the camp, but on reflection, this...definitely no longer looks intertidal. Actually, they might want to backtrack 300 meters, to the spot they passed where the riverbed was not full of rocks. Merrin doesn't really think it's a great idea to put a boat down right here.