Brought to you from the producers of “Lost”.
Lame as hell.
“The End” - WTF?!
That’s my best guess. The part when Megan and Cueball get back to the village and are able to convince everyone instantly to follow their lead seemed implausibly fast, and then…nothing, really.
Not even “Hey, the sea doesn’t seem to be rising anymore.” You’d expect at least that.
Sheesh.
There’s still a chance of a post-credits scene. 
There have been four more frames since “The End.” I wonder if something else is actually coming.
I liked it. Had to end eventually, and this is as good a point as any.
There’s been another new frame every hour since ‘The End’ but all that’s happening is the waves going up and down.
ETA: Ninja’d by Gary!
Well, there’s still something else coming, or he wouldn’t keep adding frames (even frames with nothing new), and the alt text wouldn’t be “…”.
It seems like an ongoing mystery is why the incoming water was fresh. Did I miss something there?
One of them says something like “It’s fresh, but not as fresh as a river” at one point. I think the idea is that the sea they were on was hyper-saline (like the Great Salt Lake or the Dead Sea) and “normal” sea water seemed relatively fresh to them.
Yeah, that might explain the “I can’t swim in fresh water” dialog. Not sure, I’d need to review. And I’ve been following this thing for weeks and I’m frankly tired.
Maybe a bloopers reel.
The alt text is ‘The end.’ now.
It wouldn’t surprise me if he put up something to make the last few screens loop, or possibly even something to procedurally randomly draw waves and the raft bobbing up and down, just to keep people guessing over whether it’s really over.
Seems to have stopped at 3099.
There’s still one puzzle left for me: What did they mean about the river approaching, or getting further away? I gather that it’s a seasonal river, that only flows some times of year (when there’s heavy rains upstream, or when the winter snows are melting off, or whatever), but don’t those usually work by being a trickle most of the time and widening/deepening in their season, rather than by approaching and receding?
Oh, and the bit about the steam bottle, but I assume that’s some piece of Hill People technology (mysterious to the Tribe) that they’ve salvaged from the flotsam in the river, so a full explanation isn’t really necessary there.
The River flowed into a desert, and evaporated as it went. Most of the time none of the water made it to the sea before evaporating. The basin was dry enough that the river just got shallower as it went and then just stopped at a certain point before it reached the sea. When there was a lot of rain upriver, the river could make it closer to the sea before evaporating. There are rivers like this in real life, that flow into deserts and then just vanish at a certain point due to evaporation.
OK, so the XKCD forum thread on this comic story has convinced me that the story:
–Takes place about 13K years in a post-apocalyptic Earth future (night sky star positions)
–Takes place along the shores of a much shrunken Mediterranean sea currently experiencing a Salinity crisis (Castle people’s maps)
–Takes place as the Gibralter Straits dam is once again starting to breach.
OK, now while I know past performance is no indication of future history…
Looks like the current theories (until the next one) is that the flooding of the Mediterranean 5.5+M year ago started off slowly enough for a thousand plus years (“slowly” being relative, as that article speaks of a huge, wide “water ramp” with 3x the flow of the Amazon at that stage), then boom:
Sorry, but that’s a lot of water - Peak rates of water level rise in the basin may have been as high as 10 meters per day - over 1/2 a centimeter a minute; you’d notice that. One amusing simulation video
So, is the story set at the transistion from slow flooding to rapid flooding? If so, did the Tribe of the 40 stay on their makeshift rafts for many months. Assuming similar sea levels as those of today of the Atlantic vs the future Mediterranean (fair assumption, unless this comic arc was the intro to “Ice Age: Randall’s Balearic Adventure”), the Tribe needs to reach the elevation of the Castle, or they’ll just keep getting forced higher and higher as they get flooded out - did they even come close in that little overnight tour?
Wouldn’t a dry Mediterranean be nearly uninhabitable? The average depth would be 4900 feet below sea level, and up to 17000+ feet below sea level. Compare to Death Valley at 282 feet below sea level. Wouldn’t the air temperature soar at those depths?
I started a General Questions thread re the likely climate of a dry Mediterranean here.
That’s probably why the squiggly-speaking people missed the Tribe in their evacuation alerts.
And just because it’s estimated to have taken months last time, doesn’t mean it had to take that long this time, too. The exact circumstances of the breach might be different, and our figure of “a few months” might be in error. The polyglot scholar (who is in a much better position to know) estimated “days”, and so that’s the best guess on how long it actually took in-story.