The present invention relates to an underwater drone which is an unmanned mobile which can move in the water, and more particularly to a communication system for the underwater drone which performs communication between the underwater drone and a land-based controller (or maneuvering device). The present invention also relates to an airlock apparatus for the drone which transfers the drone into or from facilities or containers, or equipment sealed (or closed) against surrounding environment. The communication system for an underwater drone includes an underwater drone (1) configured to move in the water, at least one transmitting and receiving antenna (2) provided in an area where the transmitting and receiving antenna (2) can communicate with the underwater drone (1) by wireless communication, and a controller or a maneuvering device (5) connected to the at least one transmitting and receiving antenna (2) by a wired cable (4) and configured to control the underwater drone (1).