Preserved specimens make it difficult to study nematocysts. We tested an hydration protocol on ethanol preserved tentacles of Chiropsalmus quadrumanus (Cubomedusae) during a period of ten days, and quantified the success of retrieval of information. After six days of hydration, it was possible to observe discharged and undischarged capsules of the three types of nematocysts. We conclude that hydration is a possible solution to study various aspects of the cnidome, recovering information otherwise lost.