Loch nam Madadh (Loch Maddy) is representative of fjardic sea lochs on the coast of north-west Scotland. This site is exceptionally complex. It is predominantly shallow, with deeper water only in its entrance, and wave exposure grades from moderately exposed to extremely sheltered in the inner basins. There are numerous rocks and islands and at least 22 shallow sills and associated basins. The fjardic marine biotopes on this site are more diverse than on any other known site in the EU. There is a particularly wide variety of shallow tide-swept reef and sediment habitats and communities. Some of the holothurian species found in abundance on soft mud in the inner basins, such as the sea cucumber Labidoplax media, are considered rare elsewhere. There are dense beds of knotted wrack Ascophyllum nodosum ecad mackaii and a variety of kelp forest types that illustrate the wave exposure gradient in the loch .
Loch nam Madadh is also important for reefs (bedrock and stony), sandbanks, shallow mudflats and maerl beds.
 Loch nam Madadh site summary, JNCC