They have a point. The Batter spent his time learning things for puzzles and combat, adding to his knowledge as time went on. That's why his own deaths lessened over time. But in this place he was learning more then just those things. Not all of them for practical reasons.

Seashells and rainbows.

So why not. The Batter moves to the spot that Chara indicates and starts digging. It's pretty blatantly obvious that he hasn't done this before but the Batter is going all in. And once he thinks that he's dug far enough, he'll stick his other hand in the hole to see if it's damp.

"Like this?"