A bobber includes a housing having a casing extended into a receptacle, a circuit board is disposed in the housing, a processor device and one or more light members are attached onto the circuit board, one or more batteries are electrically coupled to the circuit board. A switch device is coupled to the processor device and includes two conductor blades each having a leg extended into the casing, and a ball is disposed in the casing and engageable with the legs of the conductor blades for electrically coupling the legs of the conductor blades together, the ball is arranged to be disengaged from either or both the legs and to switch off the electrical coupling between the legs of the conductor blades when a fish strikes.