If a snake can push the bowl, sooner or later he/she will. Water sloshes or the snake is wet...water & electricity just do not mix. The best way to prevent the electrocution of your snake is to use UTH under the tank as it's designed. The only heat pads I'm aware of that are designed to be used in areas that can be damp are those designed for livestock ("pig blankets") or kennel use (whelping can be messy). I have some flat ceramic heating pads that I bought decades ago from a company that supplied them to zoos, designed to be buried by dirt in naturalistic enclosures...they too are safely insulated. Apart from using such products, I wouldn't put "UTH" within a cage, ever.