Curacha dancing crabs are a speciality of Zamboanga, at the extreme right hand bottom of the Philippines.
The first time I ate them, there, I found myself sitting at the next table to Nur Misuari, the politician then in charge of the Muslim provinces (ARMM) of Mindanao, and they were delicious (no, not the politician and his cronies, but the crabs).
Since then, of course, Muslims have gone very much out of fashion.
Nur Misuari's done a bit of jail time since, but then so should anyone who sets out to be a politician; a little bit of waterboarding wouldn't go amiss.
But we also have curachas here, in Siargao, where they are known as kanduyon or ladan.
They are good to eat, because almost all the useful stuff is in the main shell, so you don't need to fuss about too much.
They're called dancing crabs, because they sit upright in the water, on their back legs, and ponce about, like a bunch of poofs at a party.
Notice their claws; they're not a lot of use, being angled in the wrong way, quite against heavy usage. they merely use them for posing.
If these things were created, then the Great Creator made more than a few design mistakes. Thank God, He won't be held accountable.
But Thank God, He made them tasty. You can find some better photos than mine here.