Thin Ice

Thin Ice would be a new block, either in the form of a half-slab or a block as thick as Carpet, but on the upper half of a block instead of at the bottom of a block space. Basically, it’d be Ice, but like a waterlogged upper-half-slab thick. If the player jumps on it, or runs on it, the thin ice will break and the player will fall into the water below. It would generate in Frozen oceans and Frozen rivers. This would work really well with a cold-water freezing mechanic (if the player froze while in water in snowy biomes).