Why does the water turn to ice when I walk to the water in Minecraft?

Have you installed js or mod? Some js or mods will have this effect. For example, there is something called an ice ring in Ether (Heaven) 2js or mod. After equipping it, walking to the water will cause the water to freeze.

Or maybe you are in a snowfield and it is snowing, and the water just freezes under your feet when it gets cold.