One of the easiest yet most interesting dives off Catalina is Isthmus Reef. Many student divers arrive here with their classes. And since the hyperbaric chamber at the USC Wrigley Marine Science Center is just more than one-quarter mile away in Big Fisherman’s Cove, this is also a favorite site for boats participating in Chamber Day, the popular event benefiting the Catalina Hyperbaric Chamber taking place the first Wednesday of every May. They put their divers in the water while awaiting their turns to tie up to the dock in Big Fisherman’s Cove so their passengers can tour the chamber.

Isthmus Reef is favored by instructors and novice divers, not only because of its location in a sheltered area not far from shore but also because so much of it is shallow—so shallow that rocks break the water at low tide. The reef forms a rough oblong less than 500 yards long by about 275 yards wide. The water in this area is less than 60 feet deep. There’s a mini wall along the southern edge, a gentle, rocky slope off the northern.

In the early 1980s I spent a lot of time at Isthmus Reef. It was here I made my fledgling attempts at close-up photography. I’d shoot a roll one weekend, have it developed and critique my shots, then go back to The Isthmus the next weekend and shoot the same subjects until I was satisfied with the results. Not surprisingly, I’ve got loads of photos of Christmas tree worms (in every color, I might add) and it was here I took my first photo of the little shell known as Solander’s trivia. Also known as the coffee bean cowry, it’s not a true cowry, just a close relative.

On Isthmus Reef I also found a stony coral that is sometimes mistaken by novice divers for Corynactis anemones. Coencyathus bowersi is pale pink or orange and grows in clusters on the underside of rocks. While fish life— especially Garibaldi and señorita wrasse—is abundant, I haven’t seen many larger animals on Isthmus Reef. But on one perfect day in July, while taking photos of a diver wearing a full facemask with communication gear, I came across a bat ray sitting on the bottom, half hidden by green algae. The ray allowed me to take two photos before taking flight for deeper waters.

So, when diving Isthmus Reef expect to see small critters—but don’t forget to check the waters around you now and then for larger animals. You never know what might happen by.