Originally Posted by gap

I did, but I think the 90-m resolution stated in that tutorial is too low for our rocky reefs... 90 m is about the size of an islet, and I think in game we need something of the same size, or even smaller, but not totally flat.

On the web there are many heightmaps of real or fictive islands and mountains that with some resizing can be used as reefs in game. As we speak, I have one almost ready (see my post below)