If you just started TG, it might be a bit beyond you, not meant diminishingly! But you could start some experiment. The basic principle is a lake with an added surface layer between water shader and lake itself. You can mask that surface layer by a (billow) power fractal with quite strong contrast and larger sizes (40/100/5), the noise variation at say 2, and the lower 2 values also at 1 or 2. Color contrast at 1. Then set smooth surface in the surface shader, set color to white, and set the displacement offset to 1. Now you have white flat ice sheets that rise out of the water.
You can add to that with colors, extra displacement power fractals, lambert shaders for (partial) translucency, reflectivity, color the underwater area for underwater ice by a derivative of the masking power fractal, etc, etc.
The iceberg is a rounded cube with a lot of shaders to color, displace and crack it.
