90% of an iceberg's mass is under water.
There are two ways to draw an iceberg. The right one and the wrong one. The wrong one looks cooler, so that's the one I usually draw. A vertically standing block of ice shows the 90% of mass under water more clearly, but heartless gravity would definitely tip such an iceberg over on its side, so the realistic version is on the right.
If you're not sure your iceberg is right, you can always check it here.