WaterLily.jl is a new fluid dynamics simulation package written in pure Julia to take advantage of its speed and its active modelling, linear algebra, and machine learning communities. This talk will give an overview of the simulation approach, detail some of the Julia-specific aspects of the code (CartesianIndices for multidimensional algorithms and JuliaDiff for distance-function-based geometries), present a few examples, and discuss the future goals for the package.