Gearbest has the Xiaomi Aqara Smart Water Sensor for $9.99 via their daily email newsletter. Free shipping takes about a month to arrive.
This is a Zigbee sensor and works with Samsung Smartthings using a custom device handler.
As with most Aqara sensors, pairing experiences varies and you may have to be patient before it connects.
Gearbest Link with email campaign [gearbest.com]
Pairing instructions and custom handler for SmartThings can be found here: https://community.smartthings.com...r/97584/23