It took a few minutes for the boys to completely remove the objects from their hiding spots but they had already figured out what these things were. They had both seen these things on the stage during the debriefing; it was a loot crate.
Mako and Bill were both quite excited to have found a loot crate so early because Brigadier Jones did say that even though a generous amount of crates was hidden on the map, they were hidden quite well. The only reason Mako and Bill both even noticed the crate, was because of the light that shone in their eyes after being reflected off the shiny metal body of the loot crate.
After getting rid of all the vines and roots that were encompassing the loot crate, Mako decided that it would be for the best to open it when he met up with Bill so that they could equally share what was inside. The crate wasn't that heavy and with Mako's enhanced strength, he could carry it around just fine.
