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
Pairing instructions and custom handler for SmartThings can be found here: https://community.smart
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