Oh, NOW what.  Really, Esta has been having enough of a bad day already.

Esta carefully disentangles his fingers from the Sending scroll's spell structure, letting the stored magic be pulled back into the page's expensive inks; and then strides quickly outside the cave to look.

Nothing is visibly happening, yet, at least not from where he’s standing!

(The tidal bore, today when it’s approaching the monthly spring tide, moves at well over 60 kilometers per hour. At the point when he can see the wave from his current location, he’ll only have seconds left to get out of the way.)

Merrin is maybe 200 meters further downstream, on the opposite bank, and sitting down. He might notice an armored figure, if he looks in the right direction, but it wouldn’t be trivial.

Merrin, unfortunately, is herself looking out to sea, and not back upstream.

Well, he is going to look all around for any visible sources of current problems, and he is going to do this while standing in the shade with a Continual Flame lamp on his head.  Probably also Detect Magic while he's at it, if Merrin would stand out on account of being such a magical person (and gets inside the 60ft detection radius).

Neither Merrin nor her power armor nor her other gear would show up to Detect Magic, even if the latter from a Golarion perspective really look like they should, and also she's out of range.

There is a distant humanoid figure there, though, silhouetted against the horizon - 

- and Merrin is intimately familiar with her little river valley, and she does habitually scan her surroundings a bit even when she has literally no reason to expect anything interesting to happen over there because this planet has no terrestrial life larger than worms. 

At some point her peripheral vision catches a flash of...something...and she instinctively twists her head to look - 

That doesn't - what - 

Even as an unusually strong face-recognizer, Merrin is too far away to be sure she can recognize a face from here, when the person in question is standing in the shadow of the danger cave (were they in the danger cave?? why would they do that??), but there's a flash of familiarity, it's just that it's taking her kind of a long time to place because it is COMPLETELY OUT OF CONTEXT and WHAT and HOW and WHY– 

Not that it actually matters exactly who just appeared on her horrible exoplanet in EXACTLY THE WRONG PLACE at the WORST POSSIBLE TIME. 

(Superheated toilet paper were they in the cave this whole time, last time Merrin checked the radon levels were really high for some reason and her sensors were already picking up on it within five meters of the entrance...) 

She's on her feet and running. 

- and toggling the mode on the power armor where it will project her voice from a speaker, since otherwise she's basically inaudible from inside it. 

"GET OUT OF THE RIVER CHANNEL!" she shouts. In Baseline. "TIDE INCOMING! THIRTY METER WAVE!" 

She's pretty sure she's not going to cover two hundred meters of uneven treacherous limestone ground and then get herself all the way down the bank before the wave arrives, no matter how reckless she is about falling. Let alone drag someone back up it. 

She's also not at all sure it's possible for a person hearing her warning now to make it all the way up the bank in time, at this point. It still takes her half an hour and they've got less than four minutes. But she's still going to try to warn him. 

Well, that sure is an armored foreign adventurer yelling something that she thinks is very alarming, in a magically amplified voice; and that in turn is broadly the act of someone trying to be helpful, or pretending to helpfulness.  If genuinely helpful, either they recognize the Worldwound armor or they don't recognize the Asmodeanism.

"SPEAK TALDANE!" he'll yell as loud as he can.

He will already be pulling a Comprehend Languages scroll from his Holding Bag in case that doesn't work.

(Merrin is also spectacularly confused and upset and mad at Reality right now, but none of those are productive emotions to dwell on and they can go somewhere else out of her way. She's good at that. It turns out she hasn't lost the knack even after months of solitude.) 

...His voice is lost under the roar more than hers, but she can make it out enough to tell that he sounds familiar too. 

She's abruptly more sure of her face-recognizer flash of identification. And more confused and upset and she STILL DOESN'T HAVE TIME FOR THAT focus focus focus - 

Except she...can't understand any of what he just shouted back to her...? Even though it feels like she should have heard enough to catch it? 

"ESTHA! NOW IS NOT THE TIME FOR CONLANGS!* GET OUT OF THE CHANNEL!" she screams. 

(Her voice is...also going to sound kind of familiar, to Esta, even with the slightly distortion from the amplication. And the name she shouted wasn't quite the same pronunciation as his, but could be mistaken for it.) 


*This is a shorter phrase in Baseline because "now is not the time (for ____)" is a two-syllable word. 

...okay Esta is suddenly much MORE worried about what all got damaged BESIDES his Wisdom, because his brain thinks that is Mariona in unfamiliar armor and speaking in an unfamiliar language and accent.  And he doesn't know if that's because his befuddled mind is incorrectly identifying all other humanoids as Mariona, or if seeing something out of the Dark Tapestry rewrote his brain's native language into something that is not Taldane.

He will, nonetheless, cast Comprehend Languages from scroll, which takes him about six seconds, and then yell back still in Taldane, "SAY THAT AGAIN?"

Well, Merrin still didn't understand that, and she's now assigning higher likelihood that he was in fact inexplicably yelling in a conlang she's never heard before and it's not just her auditory processing failing.

(And her brain is still forming increasing certainty that he looks and sounds like her boyfriend Estha even though she does not even slightly have a theory for how or why he could possibly be on her exoplanet. Whatever he's wearing isn't even something her brain considers counterevidence, it's super doompunk but, like, it's Estha, he would.) 

She doesn't need a specific prompt to keep repeating the obvious warning in slightly different words, though. 

(She's not going to bother trying to warn him about the radioactive cave that he just left, or the UV, or the oxygen, those are not the priority right now - is he just confused and hypoxic because he was in the cave and it's having a bad enough radon-accumulation day to actually displace oxygen, it wouldn't be direct radiation sickness symptoms yet unless he was in there for multiple hours -)

"CLIMB TO HIGHER GROUND!" she shouts. "TIDAL BORE INCOMING! LESS THAN TWO MINUTES!" Maybe he can still make it, she's telling herself, though he's really in the wrong place for it, if he were on the opposite side of the tidal flats the stepped limestone bank would be pretty climbable, but near the cave it's really not...

Baseline is in many ways an incredibly weird language by Golarion standards, but the content of Merrin's warning is pretty straightforward. The only immediately-obvious linguistic differences that come across are that 'tidal bore' would be a much longer phrase in Taldane, something like "rising-ocean-tide-compressed-to-increase-speed-and-amplitude", and the time warning has some uncertainty quantifiers covered in the grammar, something like - it could be longer than two minutes, it's not her 99% confidence interval, but her 50% confidence interval is around or under two minutes, such that in a situation where it would be very costly to be wrong he should be rounding it to a hard deadline.

(Also the strongly imperative tense linguistically encodes something like a claim-to-authority, the sense that this is a phrasing where the speaker is speaking as some kind of expert who is taking charge of a situation due to having the relevant expertise - who in fact is specifically qualified to take the lead when an emergency is in progress - and who now expects and intends the listener to immediately follow her short clear instructions without asking clarifying questions until afterward, but it's sort of hard to unpack complicated linguistic implications in seconds under the circumstances.) 

All the complicated nuances of 'tidal bore' are not, actually, going to be conveyed into Esta's brain by a cute little 1st-circle spell.  Maybe you get that off 4th-circle Tongues but you do not get it off Comprehend Languages.

Esta has grasped that the canyon is about to flood.  He has not grasped the part of the compound Baseline word that invokes a mathematical concept about how compressing a passage increases the speed and amplitude of fluids traversing it according to a particular quantitative rule.

Spells which are unfortunately not part of the standard Worldwound loadout:  Water Breathing (3rd-circle for both clerics and wizards, 2 hours / caster level).

Items which are unfortunately not part of the standard Worldwound loadout:  Necklace of Adaptation (list price 9000gp, albeit in a price catalogue that is less than totally 100% trustworthy about what things would cost if you were not buying them from that particular merchant network).

Esta's Bag does have an emergency Air Bubble scroll, but it'll last, like, literally 1 minute.  It is a cheap-ass 1st-circle scroll that you carry because "it costs only 25gp", not because it is part of a clever advance strategy that requires you have an Air Bubble lasting 3 minutes instead.

Still, that ought to be enough to swim to the surface if this canyon floods...?  Timing the cast might be hard, though.  He thinks those time units sounded like "less than (somewhere around 2 minutes)" but Comprehend Languages is not really gonna do precise math for you.

Esta will give himself a 3-minute Bull's Strength, which is going to take him another 6 seconds after he pulls that cheapass scroll, so he can swim while in armor.  And then, sure, start trying to clamber up the least steep ascent he can find, with his augmented strength.  That'll save him some effort on swimming to the surface later.

...Okay, Merrin has no idea why Estha won't answer her in superheated Baseline and is insisting on speaking a conlang, and her only hypothesis is ??hypoxia?? which is not actually an explanation.

Especially when he's suddenly making rapid progress up the limestone slope! Wow! Merrin could maybe do that, but she's an endurance-specialized Exception Handling medtech, and she's not sure she could have done it when she wasn't acclimatized to the oxygen levels yet, let alone wearing what sure looks like unpowered armor for a doompunk costume rather than her very expensive Exception Handling gear. Did he start working out after she– not left. After her True Death in a plane crash. That's all he would have known until like sixty seconds ago. He's also got to be really, really confused - did he permanently die too, is the deal here that True Death is not actually a thing and actually you just respawn on exoplanets - why would Reality work that way it's so stupid – focus focus focus. 

Merrin is still herself covering ground as fast as she can, even though there's no way she's going to make it to his location in the time she has, it'll still better to be separated by fewer meters. 

She is not, in fact, planning to go any further down the bank than the high-water line she anticipates for a near-to-spring-tide tidal bore, plus a couple of meters of space for error. She can see a lot better from here, and if he's fine then he'll be fine on the opposite bank and they can awkwardly shout at each other until the water settles a little and she can safely swim over to him without getting swept 500 meters upstream in the attempt. And if he's not fine, then - well - she hasn't actually decided if she would jump into a tidal bore wave after him because surely the most likely consequence is a Stupid Accident and neither of them making it out of the river but–

Merrin's power armor is not, actually, specifically design to let her run faster than an unaided human; it also doesn't let her lift 1000 kg rocks or anything. There are engineering tradeoffs, in power armor design, and hers is meant to be maneuverable and powerful in water, and to provide her with some protection against blunt force trauma, and to still be a weight that she could conceivably carry a short distance if it had a mechanical problem and the power assist stopped working, and most of all its entire design philosophy is optimized around eking out as many hours as it possibly can on a single battery charge.

And the terrain is awful for moving fast; Merrin is used to it, and she's calibrated enough on what she can pull off that she hasn't fallen, but she's needed to slow down several times to navigate all the areas of jagged hand-sized thermally-cracked shards of limestone that would shift underfoot and send her pitching over if she were running at full speed.

...She's already sweating inside her armor, which is now pinging a gentle alarm that it's already running maximum cooling and cannot run it any harder. This is expected; the outside temperature is 43° C and the humidity is almost 100% and it's simply flat-out not specced for those conditions. 

(You could totally solve it by jumping into the tide! Imaginary Kalorm pipes up hopefully. Save your boyfriend AND avoid heatstroke! How can you say no to that?) 

The moon's position, the prevailing winds over the ocean, recent rain drainage, etc etc etc, are all working against Merrin, here. 

The wavefront, by the time it approaches them after squeezing its way through over a kilometer of narrowing river-channel walls, is moving at 70 kilometers per hour, which is 19 meters per second. It's rapidly growing in height, as several billion liters of water try to squirt down a channel which at its base, at the point where Esta is trying to climb, is only a few hundred meters wide. 

Also, the walls of the river channel around the cave are not straight, and there are several enormous boulders lodged deep into the sediment by even greater tides in even greater storms than the ones Merrin has seen yet. Esta's view more than a hundred meters down the channel is blocked, and the wave will cross a hundred meters in approximately 5 seconds. 

If Merrin tries to turn around and look behind her then she will fall on her face like a fool and possibly manage to topple head-over-heels down 40 meters of stepped limestone directly into the wavefront. 

In theory her armor, among its many functionalities, has a rear camera with a head's-up display in her helmet. It's pretty good at catching, like, unexpected movement behind her.

The small projected image taking up less than a quarter of her visual field is not great for estimating exact speeds and distances. She's not going to try to give Estha a countdown, anyway, because her model of how people function in emergencies does not think this would cause him to climb any faster. 

But she does recognize the point at which it's really, obviously, too late for her to reach him. 

She stops trying to run. She's almost level with his position, anyway, maybe only thirty meters downstream (or, well, very soon to be temporarily upstream.) 

"INCOMING!" she shouts. "STOP AND HOLD ON!" 

It's a really stupid instruction. Her mouth just sort of said it before she had vetted the content. He wouldn't be able to hold onto the rocks even if they came with perfectly designed grip-handles, because humans cannot actually do that against forces like the ones involved here. But Merrin's model of people reacting in emergencies is that they're more likely to stay calm if there's a simple instruction along with a warning and so apparently her brain insisted on generating one. 

(Also, this isn't why, because Merrin could not even slightly figure out what he was doing before with the whatever-it-was he was holding, and she doesn't have the slightest idea that Esta might now need to do anything to prepare that would take exactly six seconds. But she's calling it out long enough in advance that he will have, like, ten seconds in total between her shout and when the wall of water hits.) 

She is calling in tones of authority, instruction, and demand, of him; words that make no sense even with Comprehend Languages.  But combined with the roaring sound of water, he'll guess she should be calling for round buffs, and he'll start casting his one-minute Air Bubble.

He won't stop or lose his casting, even when he sees that this is really quite a lot of water moving very fast, and realizes too late that he needed more buffs.

Esta will not try to grab a rock.  It is very clear he could not hold to it.  Esta will try to grab his Bag of Holding, instead, because that above all else needs to not come loose from his belt.

(Merrin is so confused and has no idea what he's even trying to do and, from her perspective, he is definitely about to get knocked unconscious via violent impact with something and then drown in a totally normal length of time.) 

This is such a bad idea. If she gets smashed into rocks hard enough it might actually break her armor / or give her a concussion, the helmet will protect her from skull fractures but not the g-forces her brain would be subjected to inside her skull from an abrupt stop - and then she, also, will just drown. 

...The imaginary voice of Laeirthe is, surprisingly, not against it? She's not getting anything very clear - it always takes time and effort to run the mental voice of Laeirthe providing input - but it's - 

- this is the only thing she's done in six planetary months that has real stakes, affecting anyone but herself - 

Yeah okay shit she's jumping into a 30-meter, 70-kilometer-per-hour tidal bore.

...In a few seconds, once the main body of water is below her and she can probably actually get enough clearance in a really big leap not to just land on the sloping bank further down. (If she climbs down the bank it'll take her at least a minute even if she's moving recklessly fast, which is long enough for him to be way ahead of her and her chances of finding him quickly enough are minuscule. If she's going to be reckless, she might as well commit.) 

Caaaaaaaan she manage to keep her eyes on him even slightly after the water hits? 

Well, his Continual Flame skullcap does come with a neck strap... which looks undignified, and also makes your life worse if some creature swoops out of a cave ceiling and tries to grab the Continual Flame.  So Esta did not do up the neck strap inside the cave.  If somebody had given Esta more than one and a half moments of notice, or told him about impending rescue from a foreign adventurer his brain thinks is Mariona, Esta might have done up the neck strap to greatly improve the ease of tracking him in water.

Maybe she's got Detect Magic?  That would make him pretty easy to locate regardless.  He has got various magic items on him, and his incredibly expensive back-of-head-band in particular stays on his head Just Because rather than for reasons associated with physics.

So Esta has not done up his neck strap in order to make it easier for Mariona to locate him.

He has instead done up the neck strap earlier, just in order to not lose the Continual Flame once he is underwater; and secured a few of his other items about himself, or put the heaviest ones (like his mace) into his wonderful weight-reducing Holding Bag, while he was trying to clamber uphill.  The point is, maybe-Mariona's minimal conveyance of information was suboptimal, this happened by luck rather than due to any skill of hers, and if this actually is Mariona, Esta will no doubt have words for her later while they are going through the after-action report.  Words and pain.

Anyway!  Let's consider the effect of water moving at 19 meters per second, impacting on a 6th-circle cleric.