Based on the context and the answer, generate a question. 

Context: For some random reason ( i.e. no reason ) Alex decided that after lunch today we needed to go to the beach . Just the three of us . Keely has discovered the joy of sand castles . She made one while her daddy took care of a wall to protect it from the waves .

Answer:

The tide will come in anyway and engulf it



Why ca n't you protect a sandcastle by building a wall ?