Leaves of lotus and water lily are not easily wet because the leaves

The water-repellent nature of lotus and water lily leaves, known as the 'lotus effect', is primarily due to their unique surface topography. These leaves possess a hierarchical structure consisting of microscopic papillae coated with hydrophobic epicuticular wax crystals [1]. This micro-scale unevenness creates a rough surface where air is trapped in the depressions between the papillae [2]. Due to the high surface tension of water, droplets cannot penetrate these microscopic gaps and instead rest on the peaks of the surface structures [1]. This results in a very high contact angle (greater than 150 degrees), causing water to form spherical beads that easily roll off, carrying away dust and contaminants. While the wax is chemically hydrophobic, it is the physical micro-structure that prevents water from wetting the depressed areas [2].

Sources

1. [1] https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/lotus-genus
2. [2] https://en.wikipedia.org/wiki/Lotus_effect