Piezoelectric materials directly convert strain energy into electric energy and vice versa and are commonly used in sensing and actuating applications. They have been employed in mediums frequently undergoing vibrations, allowing harnessing of power at a small scale. Ideas of using the piezoelectric effect as a power take-off mechanism for ocean energy emerged in the 1970s and are still at a developing stage. This article overviews recent development on the application of the piezoelectric processes to the ocean field and provides a building block for future research work of ocean engineers who are interested in such possibilities. A brief discussion on the selection of the piezoelectric materials for different ocean-engineering applications is presented. Significant research projects on ocean-energy extraction through the use of these materials are then described and discussed with special scrutiny on the viability of proposed designs and their experimental or numerical validation. Various harvesting techniques in an ocean environment are categorized and compared. The challenges ahead and the outlook for success in this area are outlined.