A multifunctional metamaterial to realize broadband x-to-y cross-polarization conversion (CPC) and the absorption of electromagnetic waves is proposed in this paper. The presented multifunctional water-based metamaterial (MWM) consists of the top metallic dielectric substrate, the middle 3D printed container, and the bottom metal backplane. When the container is filled with water, the polarization conversion ratio (PCR) reaches more than 90% at 5.8-9.4 GHz, and the excellent absorption performance is achieved in the frequency band of 16.1-16.9 GHz. In addition, the CPC is achieved in two frequency bands (5.9-10.0 GHz and 14.3-16.4 GHz) without water injection. The unique properties of the proposed design are validated by experiments. As expected, the MWM simultaneously achieves polarization conversion and absorption functions, which is meaningful and consequential for multifunction and conformal stealth applications.