Previous invisibility cloaks were based on metamaterials, which are difficult for practical realization in visible light spectrum. Here we demonstrate a unidirectional invisibility cloak in visible light spectrum. By using water as the effective material and separated into several regions by glass sheets, a simplest and cheapest invisible device is realized. This device can hide macroscopic objects with large scale and is polarization insensitive. Owing to simple fabrication and easily acquisitive materials, our work can be widely applied in our daily life.