Snifit Undersand Hideout
From the Super Mario Wiki, the Mario encyclopedia
As Mario and the Mustard Café Chef are about to reach the Warp Pipe leading back to the café, they are grabbed by Snifits and placed in jail cells in the Snifit Undersand Hideout. Mario must escape the jail cell by sinking through quicksand, recover the Snifit's Card Key and the Café Key, then rescue the chef. After this, they have to take the elevator to reach the exit pipe.