First we introduce sangakus – traditional Japanese mathematical tablets. Then we give four examples of our static contemporary variants. Finally, we discuss in detail how a fifth sangaku led us to simulate the growth of water lilies, as a means of visualizing the problem. This approach lead to the mathematical field of circle packing, and made it possible to experience the visually intriguing process with different settings of the algorithm. Keywords: sangaku, history of mathematics, circle packing, simulation.