In shallower water, members of the resident sea lion colony entertain with their antics. The name collectively refers to Middle Coronado Island and the smaller adjacent Middle Rock. Several species of sea birds nest and raise young here. A small harbor seal population supports itself here. Diving depths are moderate until one moves to the west of either landmark.
Shallower depths sport rocky ledges adorned with false eel grass.
A little deeper, wildly uplifted bands of rock form deep ledges that provide homes for a wide variety of creatures. South Island Largest of the Los Coronados group, South Island is the site of the only human habitation on the islands. The Republic of Mexico maintains a small naval garrison above a cove on the lee side that once boasted a casino. Fire and the elements have reclaimed the remnants of that by-gone era. Northern elephant seals and California sea lions share a cove on the windward side that is ringed by high unstable cliffs.