An underwater ultrasonic device includes at least one first ultrasound transducer and at least one second ultrasound transducer. The first ultrasound transducer is configured to transmit a plurality of ultrasound signals and the second ultrasound transducer is configured to receive a plurality of reflected signals of the ultrasound signals. The first ultrasound transducer and the second ultrasound transducer are disposed with respect to each other. One of the first ultrasound transducer and the second ultrasound transducer is curvilinear and another one of the ultrasound transducer and the second ultrasound transducer is curvilinear or straight linear.一種水下超音波裝置，包含至少一第一超音波換能器以及至少一第二超音波換能器。第一超音波換能器用以發射複數個超音波訊號，且第二超音波換能器用以接收複數個超音波訊號之複數個反射訊號。第一超音波換能器與第二超音波換能器相對設置。第一超音波換能器與第二超音波換能器的其中之一為弧形，且第一超音波換能器與第二超音波換能器的其中另一為弧形或直線形。
