For waterproof electronics, I've had success building with these types of cases, just drill holes for wires going out, and seal them up with Sikaflex. With the transparent ones you can have an OLED display on the inside for status etc. They're usually found in your Home Depot style shop:

https://www.ebay.com/itm/Detachable-Fishing-Lure-Bait-Hooks-...