When asked to give a list of my favorite beach dives in San Diego County, I always find myself listing more and more dive spots as the years go on. Certain ones jump out more than others: the cabin cruiser off the La Jolla Cove North Wall swim buoy, Quast Hole, Octopus Reef, and God’s Rock off La Jolla Cove, the Banzai wall at the Marine Room, Numero Dos off Boomers, and Hole in the Wall off Alligator Head. However, the one I always come back to, as my all-time favorite is Fish Cannon (a.k.a. The Grotto), off Casa Cove.
Fish Cannon is a unique reef structure located at the south end of the breakwater wall at Children’s Pool/Casa Cove area. It is a pretty spectacular reef structure and only Quast Hole, off La Jolla Cove, is a comparable dive in terms of reef structure. For fish and marine life enthusiasts, it is a whole lot more though!
Fish Cannon is small gully-like structure that houses a variety of reef fish and marine life. It is essentially two-finger reef systems that create a small channel-like structure. It is an extension of the reef that starts on the shore and lies between Casa Cove and South Casa beach.
Fish Cannon is about a 40-50 foot long channel between two large rocks. There is kelp attached to the top of it and it is covered in corynactis, hydroids, and jewel anemones. Large orange and purple sponges also dot the rock structure. The marine life is a mixture of kelp and pelagic fish.
The real fun of this site is not so much the marine life that visits it, but their behavior once they do. Let me explain. At the bottom of the reef structure, you will notice that the walls are scalloped under a variety of small pebbles. Over the years, the constant surge has thrown larger rocks and carved away the scalloped edges of the rocks. Due to the surge, fish often get in the channel and are glided back and forth by the wave action. The real fun in visiting this site is to grab onto one of the rock structures and watch the fish shoot through the channel. It is like a big fish cannon! The fish are shot back and forth at incredible speeds when there is a heavy surge. It is one of the funniest and interesting things I have seen underwater.
The scalloped cuts underneath the rock are pretty interesting to explore as well. I have found a variety of rockfish and at the eastern end of the canyon I have seen several sizable swell sharks resting here, letting the small pebbles massage their backs. I also came across a seal lion once.
To get to Fish Cannon, you can take two entrances. The first is from Casa Cove when it is not closed due to the seals on the beach. Once you clear the breakwater, there are two ways to get to Fish Cannon.
The first is to swim on the surface and line up the known references. I usually use Jenner Street and the lifeguard tower to line up the site. You will see some large rocks directly beneath the lifeguard tower that signal the start of the reef. If you use these to draw an imaginary line directly west following the direction of the rocks, you will find the grotto in 30-35 feet of water.
The second way is swim out past the breakwater to the reef structure in about 20-25 feet of water. Take a compass heading on the surface directly south. The reef structure resembles seismic fault lines after an earthquake. If you follow these directly south, you will eventually run into the Fish Cannon if you stay in the 30-25 foot range.
The second entrance to the site is through South Casa. Once you enter from South Casa. Line up the large rocks beneath the lifeguard tower as noted above, and you should find it.
There are several other interesting finger reefs around the Fish Cannon. The entire area is a fun place to dive. It offers a shallow dive spot with a lot of reef structure and marine life.
Dive Spot At A Glance
Location: In between Casa Cove (a.k.a. Children’s Pool) and South Casa Beach. It is the large rock structure you see on land below the lifeguard tower extending west into 30-35 feet of water.
Access: Limited parking on street
Depths: 25-35 feet.
Skill Level: Intermediate due to rocky entry and surge.
Visibility: Average to good, averaging 10-15 feet.
Photography: Good opportunities for wide angle. Lots of small reef creatures for macro.
Hazards: Waves, surge, and currents. Rocky entry can be hazardous when waves are up. Strong rip current out of Casa Pool entrance.