Heya' Fellys!
If you were around The Island from 2012 - early 2014, there was a sign planted underwater at the Coin Cave, back when it was underwater.
It wasn't until recently that we learned that sign was put there by Teaky before he left. At first glance, it's a mad Crab with a bunch of legs, but ever since that sign was planted, a bunch of reports from Fellys with supposed proof claim that they saw a huge Crab. Unfortunately to this day, that has never been proven to exist.
When the room was renovated in 2013, the sign was redone and tried to be replicated, however, this would only last a few months since in December that same year, the ice from the record-breaking cold temperatures froze the water, and the Coral Path was forced to close, and was transformed into a cave system in early 2014, the sign would never be planted again.
At the newly opened Patuna Lake, there have been reports of sightings of a giant Crab monster living there, maybe soon it will be proven, who knows?