An iceberg is a massive chunk of ice floating in the ocean — some as big as cities, drifting slowly through cold seas. But here's the puzzle: ice is frozen water, and it's floating in water. Why doesn't it just sink like a rock?

The answer lives in a strange trick that water plays when it freezes. Most things shrink when they get cold — metal, juice, even air. But water does the opposite. When water freezes into ice, it expands — it takes up more space than it did as a liquid.

Why does ice expand? Because water molecules, when they freeze, lock into a crystal pattern with lots of empty space between them — like dancers spreading their arms wide instead of standing shoulder-to-shoulder. Liquid water's molecules are packed closer together.

Here's what that means: a chunk of ice weighs *less* than the same-sized chunk of water. Ice is about 9% lighter. And anything that's lighter than water will float on water — that's how density works.

So an iceberg floats because ice is less dense than seawater. But it doesn't sit *on top* like a cork. About 90% of the iceberg hides underwater, and only the tip pokes into the air — the floating ice finds a balance where it displaces exactly its own weight in water.

That hidden part is enormous. An iceberg the size of a building above water might stretch as large as several city blocks below the surface — a frozen mountain lurking where ships can't see it. That's why sailors call the visible part "the tip of the iceberg."

Icebergs are born when glaciers — slow rivers of ice on land — reach the ocean and break off chunks in a process called FX0. The chunk splashes into the sea, bobs up, and begins its slow drift through polar waters, melting bit by bit as it travels.

So an iceberg floats because water's freezing trick makes ice lighter than the sea, and the ocean holds it up — most of it hidden, a secret giant just below the waves.