Minecraft wiki entry for Best_biomes_for_homes, associated text: Frozen oceans have icebergs on the surface, composed of ice, packed ice, blue ice, and snow. Blue ice won't melt regardless of biome and is the most slippery version of ice.
Medium-sized iceberg (one without water pool or tunnel) can also be used as a starter house in the early game, by digging a hole in it and live inside it.
On some occasions, a structure such as ocean ruins and shipwreck may generate inside an iceberg, which makes these structures easier to reach without diving underwater.
Players don't need to worry about being attacked by drowned (especially one armed with a trident) since the surface on the frozen ocean is ice.