The limestone formation image shown at 33:44, when they first "discover" the limestone formations, is the same as the image shown at 34:30, just at a very slightly different angle, even though Josh states they had been walking for miles.
As Josh & Bill are walking through the Mangrove Swamp, Josh says that they are walking on the roots of the trees. When the ground is shown, you can clearly see planks in the on the ground covered in mud to hide them.