As we do on all expeditions, we began with a “Shakedown” dive. The first dive is primarily intended to make sure all of our equipment and protocols are working well, and to effectively get everyone back into the groove. We had already done work-up dives, but not from the Hi’ialakai this year, so we targeted a site off Lehua Rock (off the northern tip of Ni’ihau). This year, NOAA has kindly extended our depth limit too 100 meters (330 feet), so this was the depth of the site we intended to dive. I say “intended”, because when we reached the maximum allowed depth, we could see the bottom about 50-60 feet below us. Thus, we missed the drop-site, and never got to the bottom. Although our dive was effectively aborted, we still owed over half an hour of decompression time. This was largely uneventful, except for the Silky shark (Carcharhinus falciformis) that came in for a very close pass behind my head, but was gone before I had time to get my camera up and ready.
Because our dive ended early, we had some time to kill before returning to the ship to swap out for the afternoon deep diving team. Our fearless chief-scientist-leader, Dr. Randall Kosaki, suggested we eat lunch in the shade of Lehua Rock and go for a quick snorkel. It turned out to be spectacular! The water was crystal clear, the bathymetry was amazing, and the fish life was incredible. We encountered a deep crevasse about 10 feet (3 m) wide, less than 6 feet (2 m) deep at the top, and probably 60 feet (18 m) deep at the bottom. Swarming around the top of this fissure was an immense school of silvery Aholehole (or Flagtail, Kuhlia xenura); thousands of fish darting about in unison. Normally I don’t think much of this species, but in this case I was utterly amazed at the spectacle.
I was also amazed with the rock formations we saw. In addition to the dramatic crevasse, the rock was scrawled with a labyrinth of grooves cut by burrowing urchins that typically inhabit rocky shorelines. Amid the rock slopes were large “potholes”, some 3 feet (1 m) in diameter and 6-10 feet (2-3 m) deep. It is believed these holes are formed when large rocks slowly grind away on the bedrock by wave action over many, many years. I can confirm that each hole did have a rock at the bottom, but it’s hard to know whether the rock had carved the hole, or had simply fallen in.
Although we missed the deep dive, we all finished the day in high spirits after our unexpected glorious snorkeling session!