Underwater crawling and swimming type robot and working method thereof

The invention discloses an underwater crawling and swimming type robot and a working method thereof. The underwater crawling and swimming type robot comprises a robot body, a robot leg set, a propelling device set, batteries and a controller, wherein the robot body comprises a body chassis and a body upper cover; the robot leg set comprises four legs with the same structure, and each leg is composed of a thigh and a shank; each thigh is composed of a thigh first joint motor, a thigh first joint motor connecting plate set, a thigh second joint motor, a thigh second joint motor connecting plate set and a thigh frame set; each shank is composed of a shank joint motor, a telescopic driving motor, a guide cylinder, a telescopic nut, a limit stop block and a shank rod; and the propelling device set comprises five propelling devices with the same structure, and each propelling device comprises a propelling driving motor, a propeller and a locking nut. The robot disclosed by the invention can be supported by multiple legs to walk under the sea and can swim in water through the propelling devices after the legs are retracted, and the robot is wide in application range.