#inkblotart I see the shells of two dead mangrove mud crabs 

 Do you have a pic? I was thinking of coconut crabs. 

 There you go
https://i.nostrimg.com/a1b31b78a4d54080aefaf7d574e60488105b987ec1daa9b3d362d0e674800b8e/file.jpeg 

 Don't wanna mess with that critter  

 These can get quite big in Down Under 🦀 

 Without a doubt!