Mobile sinks are being exploited for various purposes for solving the hotspot problem. Thus, the mobility support technique of mobile sinks is important, and it has been studied steadily. A survey was conducted of studies of mobile sinks in sensor networks having different movement patterns depending on the applications. The related techniques were divided into three main categories according to mobility pattern: predefined, random, and control. In addition, communications for mobile sinks are strongly affected by whether there is a single mobile sink or multiple ones. Based on this twolevel categorization, an overview is presented of some state-of-the-art mobility support techniques researched during the past three years, and then the technique are analyzed according to various criteria. Finally, this survey concludes with a summary and a discussion of some future research challenges.