Another

As Rui went down, he scanned the dungeon around him in every direction he could by extending his senses as far in all three hundred and sixty degrees one by one to create a circle. Doing this every split second as he traveled down led to the creation of a tube as he went downwards, mapping circle after circle on top of each other.

He committed all this data to the Mind Palace for later revision, but he was essentially recording which paths within this mapped tube were unfilled and thus open.

On top of that, he made a great amount of progress as he went downwards by simply following tunnels that weren't filled. Covering distance that even he would not have been able to cover under normal circumstances.

He was grateful that the dungeon bedrock wasn't too porous. Otherwise, all the water would have been drained into the bedrock far too soon. Thankfully, because it didn't allow water to single into it too easily, the tunnels would be filled for a few hours, to potentially half a day.