After the terrifying incident with the Titan sub in mid-2023, we're all a little warier of submarines.
Now another sub has gone missing - and it's a pretty mysterious episode.
The sub in question was an unmanned underwater vehicle (AUV) called Ran and owned by the University of Gothenburg.
This means it was a research vessel rather than one for recreation - and it was looking into the Thwaites Glacier in the Antarctic.
This glacier holds massive scientific interest, for pretty depressing reasons - it's widely expected to collapse and break off into the sea at some point in the next decade or sooner, potentially causing a catastrophic rise in sea levels.
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This ticking time bomb is why some scientists call it the 'Doomsday glacier', which has to be one of the scariest names a natural phenomenon can be given.
Ran had already explored the underbelly of the Doomsday glacier before, and was returning for more probing when it ran into issues.
It looks like it might have got stuck and its battery went flat, leaving it unmoored and unpowered under a huge glacier, without a precise location to home in on. This means that there likely won't be a rescue effort to retrieve its onboard data.
Project leader Professor Anna Wåhlin from the Department of Marine Sciences at the University of Gothenburg said in a statement: "It's a bit like looking for a needle in a haystack, but without even knowing where the haystack is.
"At this point, Ran's batteries are dead. All we know is that something unexpected happened under the ice. We suspect it ran into trouble, and then something prevented it from getting out."
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Ran has built-in navigational systems that should let it automatically route itself back to its starting point regardless of what happens, so this system must have somehow failed.
Of course, this doesn't exactly explain how the submersible ran into trouble, or what caused that trouble, and this sort of ambiguity will doubtless fuel speculation for a while.
Still, Wåhlin has an optimistic way of looking at the whole situation: "The data we receive from Ran is unique in the world, and of great value for international research. At the same time, the stakes are high, we knew something like this could happen, even that it's a likely end for Ran.
"Personally, I'm of the opinion that this is a better end than having the AUV aging gathering dust in a garage."