Santa Barbara Island (SBI) has an awful lot going for it. It’s got sea lions (obviously—and probably its best-known feature) but it’s also jam-packed with great dive sites all around its perimeter. One of my personal favorites is called Black Cavern.

Now let’s understand from the git-go that this is a somewhat advanced dive as it involves depth and an overhead environment. So this is probably not a site you want to try fresh out of your Open Water class. But that doesn’t mean once you have a respectable number of dives under your belt, or can go with an experienced and qualified Instructor or Divemaster, that this is out of your reach.

The site lies along the western side of SBI, between Three Sisters and Webster’s Point. There are actually a series of caverns, but what is presumed to be the biggest one (and the one that’s dived the most often) is Black Cavern.

Most of the boat captains who dive this are able to drop the anchor right into the opening of the cavern at roughly 100 feet. This makes it an “easier” dive, but don’t let the ease of finding it lull you into a false sense of security. Sometimes captains will drop anchor on the part of the reef that forms the ceiling of the cavern, around 60 feet, which means you’ve got to swim over the edge and down to find the entrance. In either case, you really need to watch your depth, bottom time, and—most importantly—air.

Simply put, the caverns seem huge. Although I’ve never measured it, you can easily go in four or five divers abreast. There’s plenty of room between the floor and the ceiling, so there’s no reason or excuse to be bouncing off the bottom or pushing off the top.

Once inside, you’ll discover that the place is crawling with life. There are certainly the normal lobsters you’d expect to find hiding in the cracks and crevices, but you’ll also spot some sea fans, gorgonians, starfish, sponges, and other life that can exist inside a fairly dark area.

Now comes the tricky part. By definition, a cavern means you can always see daylight. As you go further in, the floor rises (and turns a bit) and it would appear that what you’re really entering is a cave. But take a closer look because you’ll see a faint glow in front of you. This is the exit. And you need to make a decision as to whether you want to turn around and go out the way you came, or if you want to push all the way through and come out the back end.

In either case, you really need to keep an eye on air consumption. The cave diver’s rule of thirds should certainly apply here: one-third of your air for the trip in, one-third of your air for the trip out, and one-third for emergencies and contingencies. But if you started the dive with 3000 p.s.i., don’t think this means you’ve got 100 p.s.i. in and out. Your calculations should be based on the amount of air you have when you start your entry into the cavern. Once you hit that one-third mark, if you haven’t made it halfway through, turn around. If you’re past the halfway mark, you can continue through to the end.

But it’s a really interesting dive with an interesting finish because if you come out the back end and now come back up and over the ceiling (about 60 feet deep) to get back to your descent area, the plain that you’re on (really the topside of the ceiling) is thickly covered with brittle stars, covering about every inch of space.

Due to the depth and presumed air consumption, you’re not going to have much bottom time at Black Cavern. But it’s a really interesting dive, fairly unique to our area, and—if your experience and skill level is up to it—worth doing. Check it out the next time you’re at SBI.