TAKENAKA ENGINEERING CO., LTD.

［Discontinued］Wireless leakage sensor with buzzer (Spot type)　EXL-SWB1S

Since it has a buzzer, even if multiple units are registered to the same channel of the receiver or receiving unit, you can find out which sensor is detecting by the buzzer sound by going near the site.
The case is waterproof (everyday life waterproof structure: equivalent to IP 67), so it will not break down even if it is submerged.