This paper provides a method to localize an underwater beacon in real-time and overcome the challenge of SNR due to ambient noise and multiple reflections. The signal of beacon is a 4-ms pulse per 0.5 second, 1 second or 2 seconds, and the frequency is 25 to 40 kHz in 0.5 kHz increment. Details of this information is not disclosed until the day of the competition, which adds to the challenges. The algorithm for calculating direction where target signal is coming from is time difference of arrival(TDOA). In order to receive the time difference, we use two hydrophones at two different positions. After getting the time difference, incident angle can be calculated consequently, thus the direction which the target signal is from can be determined.