She can manage a lot more easily without the boxes! It's still an intense workout, keeping her balance while the silty mud tries to swallow her boots, but she can do it. 

Okay. 

Merrin does not think she can afford to risk another laden trip up the slope.

(For one, if she gets caught in the wave, she...will have a significantly better chance of surfing it upstream and surviving the adventure if her suit has the hydrodynamics she's used to. She's never actually done a training that involved challenging water conditions with several boxes of gear strapped to her suit and completely ruining its streamlined profile, let alone what more or less amounts to attempting to surf a tsunami. 'Getting caught in the tidal bore' is still a huge risk, to be clear, her challenging-water-training took place in the open ocean and not in a river channel full of dangerous obstacles, but she might be able to manage it if she can trust her power armor's water functions to be at top performance.) 

...She's genuinely pretty upset at the prospect of losing the last two boxes. The backup medical supplies aren't just useful for emergency medicine; she could turn the gauze into textiles for clothing, use the sute needles as...fishhooks? does this planet have actual fish or just simple invertebrates?...she hasn't thought through everything that could be improvised into something, but eight boxes of gear is all she has and it's viscerally painful to think about losing it. And her armor box is, in addition to a safe place to keep her precious and essential armor suit, an insulated, waterproof, and highly durable storage location for arbitrary objects. She doesn't have the manufacturing ability to make any more. 

The boxes might wash upstream and be findable later? If she's willing to spend the next several months looking? They're really durable; Exception Handling toughened wilderness gear is dath ilani manufacturing at its finest. The contents might pick up some damage if exposed to extreme g-forces, but the medical supplies in particular are not very fragile and are packed in a way where they ought to survive being literally airdropped from 5,000 meters without a parachute.

The main cost is that she would have to scour every meter of riverbank, and meanwhile they would move with every tide, and...yeah, she might find them before she dies here, or she might not. 

...Can she somehow wedge them in a place where they'll still be there once the tide drops? Put them somewhere where the incoming tidal bore will just push them harder against the wedging surface, and hope that the speed and turbulence of the current from the outgoing tide is less intense and they stay put? 

Well. She's actually pretty much right beside the river channel. And the very bottom of that channel, already submerged, is going to be the place least disturbed by the violently incoming tidal waters. And she is wearing a suit that's designed for underwater operations, and taking a break from the gravity might actually count as a bit of a rest. 

She slips down into the water. 

(It doesn't feel cold. It must be frigid - the suit will have a record to peruse later - but the armor takes care of heating.) 

....It's beautiful. It's really, really pretty. 

It's an ACTUAL EXOPLANET with ALIEN LIFE!!!!!!!! Merrin has not had a huge amount of time to think about the positives of her extremely ridiculous current situation, but it continues to be really cool!!!!!!!!

There are more, and larger, mollusc-like organisms down here. Some of the shells - a little like clamshells or oystershells in shape, but remarkably dense and heavy and thick - are slightly open, with delicate fronds waving, but if Merrin's shadow passes over them - or maybe it's not her shadow at all, it still happens even in the dimness under rock overhangs, maybe it's the water disturbance vibrations of her passage - they immediately snap shut with rather a lot of force. You could lose a finger that way. If Merrin tries tugging on them, she'll find them glued to the rock with a very impressive stubbornness; it would take a sharp knife, or possibly underwater explosives, to dislodge them from their anchors.

There are algae biofilms plastered flat against the stone everywhere, and in a wider range of colors – not just the deep maroon-purple-black, but vivid crimson reds and even deep rosy pinks, the photosynthetic pigment present with less of the melanin-analogues for UV absorption. 

There are...tubeworms? Short, segmented, heavily armored bases, with long delicate tendrils waving in the water that, again, instantly curl up and vanish inside the armored tube when Merrin's shadow passes over them. 

There aren't all that many mobile fishlike organisms. A few semi-translucent wormy things, no larger than Merrin's pinky finger, that stick close to the rock surfaces and corkscrew into crevices when her movement disturbs the water near them. She sees one larger organism – a segmented-worm body with bilateral rows of flat paddle-like limbs, like a bizarre combination of a fish and a centipede. It's about twenty centimeters long and swims slowly, radial mouthparts opening and closing in the algae-hazy water. 

Cooooooooool!!

(This planet is...probably a lot earlier in the history of complex multicellular life, Merrin thinks? It would make sense of the lower oxygen, if there just hasn't been enough photosynthesizing biomass for long enough to complete the shift from a low-oxygen to a high-oxygen atmosphere. The centipedefish is the only organism she's seen that looks like it has a genuine nervous system, and probably not much of one.)

There are also larger, thicker mounds that, on closer examination, seem to be some kind of sea sponge. They're flattened, not structured like coral on dath ilan, but they're hardened - calcium-like deposits, or some kind of very tough hard keratin-like protein, or both, or something else entirely, Merrin has no way to determine the exact chemical composition. 

There's also seaweed! It's the most complex and structured plant life she's seen by far. It's sort of kelp-like, with a root-system anchor and fronds that extend into the water column. No sign of air bladders for buoyancy, though, and the fronds mostly hang downward from rock overhangs into the current, though they're anchored in ways where it doesn't look like it would risk dislodging them if the incoming tidal current were to tug them the other way.

Unsurprisingly given the forces they're regularly subjected to, the root-anchors are huge and extensive. If Merrin swims up close and paddles against the gentle river current to stay there for a while, and uses her headlamp, she can see that the roots aren't just stuck to the rock, but at dozens or hundreds of points seem to have eaten into it. This particular patch has an anchored-root-system base a good two meters across, securing a bundle of fronds less than four meters long. 

They're very secure. Merrin can grip a frond and plant both feet and use the suit power as well as her own muscle strength to pull as hard as she can, and it doesn't budge at all. 

Hmmmmmmmmmmmmmm. 

...Merrin is going to swim downstream a bit and check out some of the other seaweed patches. 

Here's one where the root system is anchored on the floor of a shallow erosion-depression, not quite an underwater cave yet but on its way there. There appear to be several of the plants, with root systems overlapping and reinforcing each other. The fronds are particularly long, maybe as much as five meters, undulating in the current; if the current switches, they'll be plastered against the arch of the would-be cave. 

Hmmmmmmmmmmmmmmmm. 

.....The straplike fronds are flexible enough to tie into knots. And the root system has points where one could slide a loop of paracord under a particularly thick root and secure additional ropes. 

Yeah. Merrin thinks she has a scheme for where to attempt to secure her last two crates. Though she had really better hurry. 

When she re-emerges, she still can't see any ocean, and she doesn't hear the roar of an approaching tidal bore wave, though of course at the point when she did hear one it would be at most minutes away. 

....Merrin has an unforeseen problem, which she could have foreseen if she had thought about it for ten entire seconds. 

The full box of redundant medical supplies is neutral-to-negative buoyancy. Merrin won't have any trouble swimming down to 10m of depth with it and holding it against the current while she ties it into place with the 10m of paracord she has in her front pouch. (Because she was being dumb and did not think through the fact that she might want to secure anything at the bottom of the river channel, and she has a lot more paracord than that but it's at the top of the riverbank, which right now might as well be the Moon.) 

The empty power armor crate is sealed full of air. And thus rather buoyant. She does not think she can easily haul it deep underwater, and its buoyancy will strain the attachment points even when there's no current. 

...She'll swim down with the first box and secure that and use the time to think of solutions. 

The seaweed frond material is really remarkably tough. Merrin tries dissecting one down the middle to split it into two halves, so she can knot it in more places without using paracord, and her small multitool knife is having a lot of trouble with it. (She has sharper knives, and a lightweight hatchet, but both are in the toolbox at the top of the hill.) 

She gives up on that plan and just knots what she has; it's a thick, flattened, slightly twisted ribbon, as wide as her wrist and almost a centimeter thick at the center, leathery rather than woody, and she thinks there's silica incorporated too. The edges of the ribbon are sharp and it's a very good thing her suit gloves are sturdy. 

....And then she's going to saw through one frond at the base, to try to take with her. Because this planet might not have any trees, but this ultrasturdy seaweed might have real promise as a building material. She'll want to see what it's like when it dries. 

By the time she makes it back to her last remaining crate, her suit clock thinks it's been 13 hours and 20 minutes since dawn. Eyeballing it from this angle, it looks like the sun is nearly at its zenith. 

The temperature is up to almost 18° C. The tidal flats must be getting even hotter; some areas are steaming as water rapidly evaporates. 

The moon is still a long way behind the sun, in terms of making its arc across the sky. Not a spring tide, assuming that "spring tides" on this planet also correlate with a lunar-solar syzygy. She still can't see or hear the ocean. 

Okay. 

She has two options: 

- Try to carry the crate up the hill - it's not heavy - and, if she hears the roar of ocean approaching, ditch it for streamlining in case she doesn't make it and has to surf 

- Load it up with rocks???? 

...There is, unfortunately, a complete lack of nicely sized stackable rocks, down here. Some of the "exposed rock" might belong to large boulders embedded in sediment, rather than being directly attached to the bedrock, but she doesn't know which ones to try to dig up, and they might all be too big to even fit in the crate. Any small rocks have clearly been thrown around by the tide until they were eroded down to pebbles and grit. 

(Filling it with water - with pure water of neutral pH - might not irreversibly degrade the lining, but it's not really meant to be totally waterproof from the inside. She has lots of collapsible-waterproof-container water storage; she wasn't supposed to need to adapt the boxes as cisterns. And, of course, she hasn't had a chance to fully analyze the seawater; the suit has sensors for pH and osmolality, once she gets around to digging around in the menu, but it was not designed to give her a full analysis and readout of the chemical composition of seawater on ANOTHER PLANET. Also, if she wanted to weigh down the box by filling it with water, she would have to remove the spare suit battery and rig something to carry that, if she wants to use it; it's water-resistant, dropping it briefly in a puddle wouldn't destroy it, but it's really not specced to survive sitting around in mineral-filled seawater for days.) 

...Okay. Merrin's climbing-relevant muscles do actually feel somewhat rested, after taking a break from the gravity and using different muscles.

Harnessing the empty box to her back and going as fast as she can, that's what the plan will be. (And the seaweed frond she cut is wrapped a few times through the harness webbing to secure it along with the box.)

It takes significantly longer. Before, when the ground was frozen and she wasn't so exhausted, she'd been able to make it from her landing spot to her box cache at the top of the bank in about 100 minutes. Exhaustion alone would probably have brought it to two hours. 

This time, three and a half hours pass - it's now been 16 hours since dawn, the sun is clearly trending back down in the sky, and her suit has flipped over to cooling mode because the outside temperature is up to 28° C - and she's still not up to the highest debris line, let alone all the way back to her cache. The stone is dry, here, it's no longer slippery, and she would be making faster progress, but it took her more than two hours just to cross the silty tidal flats, and she's very close to exhaustion.

And now she can hear a roar in the distance, and feel the vibration of it conveyed through the rock and into her bones. 

Perhaps Merrin is not quite on the edge of exhaustion after all! The adrenaline produced by sheer terror for her life can eke out a bit more speed! 

(She's really close to what she thinks is the true high-tide line, and she might already be above the current high-tide line, if she's right that this isn't the highest the tides will get. It doesn't quite seem worth ditching the box, especially since it's not really slowing her that much at this point, on stable rocky ground, and she would really like to have the spare suit battery for tonight.) 

She makes it, with - probably minutes and not literal seconds to spare, but still - and she flops down beside her haphazard pile of boxes, and she watches the tidal bore wavefront roll in.