Was wondering what others have done to measure temperature in a liquid, the water temperature in my hot tub in my case?

Have put a DS1820 series inside a 12” of ¼ plastic tube, and capped it. But eventually water leaks in. Then went to Home Depot and bought some “Scotchkote,” dipped the plastic pipe in that, let it dry 24 hours and that seemed to work for quite awhile, but it eventually it started to leak again.

There are two other options I was considering and that was ¼ copper pipe with a soldered or encasing the DS1820 in epoxy inside a glass test tube. But I really need the 12” length to handle the varying water levels in the tub.

Looking for suggestions