Luffy discovers that water solidifies Crocodile's sand body, allowing Luffy to land physical hits. In this chapter, Luffy famously uses a large barrel of water (Mizu Luffy/Water Luffy) to fight back.

The battle takes place at the Alubarna Palace . While the Alabasta Royal Army and the Rebel Army are clashing in a bloody civil war outside, the true fate of the kingdom is being decided on the palace roof.

It highlights Luffy's "battle genius"—his ability to think of unconventional ways to win against overwhelming odds. Safe & Official Ways to Read

This was one of the first times fans saw a Logia-type user (previously thought to be invincible) defeated by a natural elemental weakness rather than Haki (which hadn't been fully introduced yet).