Roca Partida is not so much an island as it is a small lava plug from an extinct volcano that has otherwise been eroded away into the sea. This rock pillar is only about 300 feet across at its widest point, and it descends almost vertically to a depth of 250 feet, where only then does it begin to take on the topography of a typical mountainous volcano. Situated in the open ocean, 60 nautical miles from the nearest land, the only inhabitance of this failing island are a great many birds which is evidenced by the snow-like white shrouding of all but the most wave-beaten rock. While there is not much in the way life above the surface at this site, it is known among divers for its nearly constant traffic of Manta Rays, Sharks and Tuna. Roca Partida is, in fact, generally thought to be the best dive site the Revillagigedo Archipelago has to offer.
Because of the remote and exposed location of this dive site it is important to have good weather or the swell becomes too large, and the site undivable. So, when the weather report came back fovorable for the next few days the decision was made to pull anchor and begin the 60 mile trip to Roca Partida, where we would spend the next few days diving. Because these islands have not been re-charted since the advent of GPS, the moving map displays on the ship are not always totally accurate and the crew prefers not to maneuver the boat around the tiny island at night if it can be avoided. I, myself, got somewhat confused at one point when I turned on my little Garmin GPS and found that it had me placed right on the beach of Socorro when I was quite clearly standing on the deck on the Nautilus Explorer! Anyhow, the trip would take about 12 hours, so we decided to leave Socorro for Roca Partida after dinner so that the sun would be up by the time we arrived.
To my surprise, the dive briefing that night included very little of Sten’s humor and joking, but instead a lot of stern warning about not loosing visual reference to the topography and the importance of surfacing near the island. Because it is basically an open-ocean dive site and there is no shotline, a diver that surfaces very far from the Zodiac or skiff is difficult to see, and can easily become lost at sea. While we all carried surface marker buoys (SMB’s) and mirrors to mitigate the risk, the warning was clear. “Never lose the topography underwater. If you become disoriented, surface without a safety stop and inflate your SMB.” Sten saved the most chilling warning for last, reminding us that if we became lost the only Boat looking for us would be the one we were on, and that if we were not found by dark we would not be found.
That night I did not sleep well, and woke up entirely too late to get my rebreather configured to make the first dive. Instead, I lounged around, drank coffee, and leisurely pre-dove my rig. Rich, on the other hand made the first dive and mentioned that maintaining counterlung volume was difficult above 30 feet because of the substantial swell. We both made the decision to dive open circuit at this site and I carefully packed up my Meg beneath my bunk.
My first dive of the day was great fun, but something in my brain forgot what it was to dive standard SCUBA gear, and I emptied my tank to 500 PSI after only 45 minuets in the water. You can breathe as hard as you like on rebreathers, but not so on open circuit. I had borrowed my gear from the boat, and was surprised to look down and see that my borrowed dive computer, a TUSA IMPREX, read that I was at 155 feet! My trusty VR3, a dive computer that I have depended on for years, and one that has been used on many a gnarly tech dive read only 100 feet, so that was the one I decided to trust. The IMPREX racked up quite a deco obligation, so I went ahead an cleared it while playing around in 30 feet of water or so. The 30 foot level turned out to be the most interesting anyhow because we saw a large Manta, some White Tip Reef Sharks and some large Tuna towards the end of the dive. It was difficult to maintain a constant depth, however, because of the strong surge and swell.
The second dive of the day was much the same as the first, except my camera ran out of batteries about half way through the dive and I did not consume nearly as much gas. By this time I had ditched borrowed regulator in favor of another borrowed regulator, and no longer had to suffer the greatly exaggerated depth displayed by the IMPREX. I swam a total of two laps around the island at a maximum depth of 100 feet, but saw little other than a few sharks and large groups of bait fish. The entire dive lasted about 45 minuets.
By the third and final dive of the day, it was getting dark, and again, we saw only sharks. My camera was working perfectly, but I had too little light for much other than macro shots on the rock. I did get some interesting pictures of little shark dens where juvenile White Tips would gather to rest, sometimes among Moray Eels. Again, I circled the island two times at a maximum depth of 120 feet, and the dive lasted 45 minuets.
Roca Partida did seem to be a great dive site, but at the end of the first day my feeling was that it had been hyped quite a lot. We had only seen Mantas on the first dive, and I was a little unhappy that I didn’t have any helium with which to dive down to the are where the pillar leveled off at 250 feet. The conditions were rough, but not nearly so difficult as had been let on, and a part of me wished we were not spending two days there. I had no way of knowing at the time, but the next day would do a lot to change my mind!