Sharky Day on the North Coast

Second dive on a pinnacle outside of Airport Cove yielded some nice lings and my first sighting of a blue shark. It was 7' to 8', I saw it 15 seconds before it saw me, and there was quick agreement to go in opposite directions.

I thought I'd relate the rest of the story as it fell together over the following weeks.

The shark encounter started at 50' with me swimming along the flat top of a fairly large pinnacle that bottomed at 100'. This formation is actually two pinnacles separated by a cut that bottoms at 90'. The plan was to cross from one pinnacle to the other and I was headed in that direction.

When I came to the edge of the pinnacle, I started to pull myself over the edge and found something at my belt was hung on some kelp. So I backed off and untangled while sitting atop the pinnacle. I'd gotten a good glimpse over the edge before backing off and knew I'd be going down a sheer wall about 40' high. Visibility was good enough that I could "sense" the bottom at 90'.

On the second attempt to pull myself down the wall, I immediately sensed some movement off to my left and froze with just my head and shoulders hanging over the edge. Out of the gloom and at the edge of visibility, I could see a shark shaped shadow swimming toward me. It was 5' or 10' off and down the wall and was going to pass right in front of me. I could clearly make out the outline of the animal and I could see it was swimming slowly with the fluid tail sweep of a shark. As it approached, I could make out the shape of the head from slightly above and, as it passed, I noted that it looked very husky through the shoulders. I estimated the overall length at 7' to 8' and jumped to the conclusion it was a blue shark. I was certain it wasn't a white and that was all I really cared about. As the tail passed by, I got a very good mental image of its shape and symmetry.

Then I remembered my small dive light and thought to illuminate the shark. When I swung the beam toward the shark, it responded violently. First, it lurched half it's body to the left and then back toward the right. In the wink of an eye, it'd taken on a convoluted S-shape and, in the next instant, kicked into high gear. Like it'd jumped to warp speed, it was gone.

At that point in the dive, I stopped and spent a few moments contemplating. While thoughts about the shark were flashing through my mind, I worked out the question of whether to continue over the side and down the wall. In a less than impressive display of mental agility and internal fortitude, it took me 30 or 40 seconds to decide to do a 180 degree turn and go back the way I'd come. I was hoping to find the other divers in the vicinity, soon did, and spent the rest of the dive furtively looking over my shoulder. My air consumption was less than ideal and, after signaling the other divers, I headed home. On the surface, I discovered the boat was 150 yards away and, blue or not, I didn't enjoy that swim in spite of the record speed I set doing it (thanks, Brian, the Black Diamond generates a lot less drag).

An underwater shark sighting off northern California is exceedingly rare. This was my first in waters north of San Francisco and that accounts for part of my confusion over exactly which species I saw. My other excuses include the short duration of the encounter (15 - 20 seconds), the cryptic coloration of the animal, and my vantage point (slightly above and off to the side) against a dark backdrop. Based almost entirely on length alone, I concluded it was a blue and I looked forward to checking out some of my reference books when I got home. I had a good image of the head and tail plus a strong impression about the overall proportions.

The books quickly eliminated any possibility it was a blue. The tail simply didn't match. What I saw was a slightly assymetrical tail with the distinct but unexaggerated flap structure at the top of the tail fin that is typical of many sharks. That tail also didn't match either the six- or seven-gill sharks. Next possibility, a soupfin shark. The tail fit but the bulkiness and overall length was too much for a soupfin. Digging deeper, I found a likely candidate, the Salmon Shark. Right tail, right head shape, right proportions, right size. The only question, in my mind, was whether or not Salmon Shark are likely to be encountered near shore; my reference book labeled it as pelagic. So I put a query out on the shark-l list describing pretty much the same thing I described here and asking whether the location worked for a Salmon Shark.

I received a number of responses but David Powell of the Monterey Bay Aquarium was the most convincing. Basically, he pointed out a few details I'd missed. First, the shape of the head and the tail matched the Lamnid sharks. So soupfin and salmon were reasonable possibilities. But the soupfin is too small (both in length and in girth) and the salmon is pretty rare off northern California. Moreover, the salmon is unlikely to be encountered close to shore. So, if it was a salmon shark, it was an exceedingly rare encounter. He went on to point out that white sharks are also Lamnids, they're fairly common in California waters, and they prefer patrolling closer to shore. His conclusion was that it was a white shark and, at 7' to 8' in length, it was probably 2 to 3 years old.

End of story.

A couple of side notes from this encounter.

If it looks like a shark and moves like a shark and you're diving northern California, you can probably lay odds on it's being a white shark.

The cryptic coloration of these animals is quite incredible. At my 50' depth, the top of the pinnacle was nicely illuminated and, looking down the side, enough light was penetrating to see details quite a ways down the wall. It was darker looking down and it was this darker background that the shark moved across. Against that background, I was unable to _see_ any details on the shark other than the tail as it passed right in front of and slightly below me. Everything else was a silhouette. It was like seeing a three dimensional shadow move past you 15' away. Quite eerie and very impressive.

The other thing I witnessed was a demonstration of how fast these animals are. If you can imagine something at least 7' long and a few feet across with the acceleration of a bottle rocket, you're in the ballpark. Without reservation, I recommend not trying to pet a shark.

{norcadiver@sonic.net}