Research on deep seawater is of great importance to marine chemistry, biology, and climate science studies. Sample analysis is the fundamental and most effective method for deep-seawater research, and it is essential to collect high-quality water samples for the scientific community. Over nearly a century, various deep-seawater samplers have been developed to meet different research needs. This study provides a comprehensive review of deep-seawater sampling technology and instruments to highlight the associated research background and importance, summarize sampling principles, and categorize typical samplers. This review focuses on the key technologies that deep-seawater samplers perform, including sealing, pressure maintenance, and temperature maintenance. Finally, prospects are presented in terms of three aspects: high fidelity, long-term series sampling, and precise sampling using autonomous underwater vehicles. This review can serve as a reference to achieve the precise sampling of deep seawater with high fidelity and spatiotemporal resolution in the future.