The Honeywell Home RCHW3610WF1006/N Water Leak Detector is on sale, lowest I’ve seen and CCC says it’s the lowest it’s been.
This saved me from a big flood damage bill when my water tank started leaking over night.
I prefer this over others because it has a long water sensing cable, loud alarm, phone notification and the base also detects water as well.

Amazon product: Honeywell Home RCHW3610WF1006/N Water Leak Detector
Customer Reviews:
I live in one of the highrises in Vancouver. Our strata recently started asking us to have $250k insurance for water related damages. This resulted from high number of instances in the building caused by water leak related damages. | We got 4 of these units 1 for kitchen sink and dishwasher another for laundry and two for bathrooms. These devices connect to our home wifi and send notification as soon as they detect water. I tried by submersing the cable in water and it immediately started sounding loud sound (similar to smoke alarm) on device as well as sent a notification on my phone and email. | This should alert us in case of water leaks that if not addressed to soon enough will cause our insurance company to pay for huge claims. | I wish thought that Insurance companies provide some discounts on having such smart devices at home.