The Coronado Islands (Los Coronados) lie approximately twelve miles nearly due south of entrance to San Diego Bay. On a clear day, you can easily see them from Cabrillo National Monument on Point Loma. The Coronados are located WSW of Tijuana and about 8 miles offshore from mainland Baja California. All Mexican laws apply, including fishing regulations. Keep in mind that if anyone on board hunts or fishes, then everyone on board must have a Mexican fishing license. Also, in Mexico, spearfishing can be done by freedivers only—not on scuba. Finally, the U.S. Coast Guard will still help you, but don't forget that you are no longer in the United States.
Above is the view of the Coronados approaching from the north. North Island, the outer—or westernmost—island comes into view first, followed by the two small islands which make up the Middle Grounds, which are close upon South Island. South Island is by far the largest. On the back side of South Island, facing Tijuana, you'll find a number of old buildings at Puerto Cueva Cove. There are lighthouses at both the north and south ends of South Island.
The eastern side of each island is the leeward side, protected from the dominant ocean swell pattern. The western sides can be dived on very, very calm days. One of the most protected sites at the Coronados is Moonlight Cove, at the larger middle island. Longshore currents here can be a factor, so pay attention to whether it looks like the water is flowing quickly past the islands.
As far as marine life goes, look for a lot of the shallow rock reef creatures you would expect to see up in San Diego, just in better vis and looking less harrassed! In addition to lots of garibaldi, blacksmith, senorita, rockfish, etc., you may see an occasional lingcod. Watch for moray eels. You may also see sea lions and/or harbor seals. Instead of just sea stars, you'll also see sunflower stars (many more arms and larger). Everywhere you will see lots and lots of sea urchins, small purple ones and much larger black or dark red ones... even tiny little white ones.
Lobster Shack sits just past the northern tip of North Island on the eastern side, in a very small cove. There used to be several shacks just onshore, apparently used by lobster fisherman. This is a good anchorage, although you'll likely be vying for a good spot with the local commercial dive boats. Underwater you will find a boulder-field of large boulders down to about 40 or 50 feet, then sand. Look for a small school of triggerfish and moray eels in the crevices between the boulders. Also check for the occasional elephant seal up on the rocks.
At about 60', down in the sand towards the southern end of the little covelet, is the wreck of an approx. 40-foot cabin cruiser. Several years ago the owners of this boat had it on autopilot at night and failed to see the island. Now we have a good wreck dive site! The Blue Escape (dive boat, pictured above) here sits just about above the wreck.
The Lobster Shack is at N 32 26.541, W 117 17.734
The Keyhole sits near the southern end of North Island, where several small openings exist in an archway connecting the main body of North Island to a smaller peak just south. Even on calm days the ocean swell, unobstructed for many hundreds of miles, pumps through these passthroughs. This is not a site for the inexperienced and not a site for anything but calm days. The rock formations here are very dramatic. Gorgonian and sponge life is very healthy. Down slope from the southern end of the island you will find purple hydrocoral and huge fields of discarded shells.
A closer view of one of the holes in the archway at The Keyhole.
Here we're looking north from inside Moonlight Cove at the small beach in the corner of the L-shaped cove.
Moonlight Cove is a fairly shallow dive spot, and a great, sheltered place to hide from swell or current or just to have a calm lunch on the boat. The coast here is an upside-down "L", long on the north-south side. Underwater you'll find a boulder-field down to about 20 feet, then sand with occasional large boulders. You can follow the sand sloping down slowly to the east, down to 40 or 50 feet, but beware of getting out into currents between the Middle Grounds and South Island.
Two underwater arches can be found east of Moonlight Cove; one due east in about 30 feet of water, and the larger one at 10–20 feet through the NE corner of the "L" which makes up the Cove.
Here the Ocean Express has divers in the water at Seal Cove, on the slightly more exposed northern side of the larger middle island. Just behind the Ocean Express—on the other side of that rock—is Moonlight Cove.
GPS coordinates are N 32 25.211, W 117 15.531.