Today we start a period of high frequency sampling for water chemistry. We are trying to have divers out on the reef every 30 - 60 minutes for the next 18 to 24 hours. This required that we use one of the habitat technicians in the dive rotation to fill out the buddy teams. So, we have five divers with each of us standing a 6 hour watch in the water.

The excursions will be out to our deep current meter site (105 feet/ 32 m) where we will take water samples in an attempt to capture the nutrient signals of the internal bores. Most of the first part of the day we did half hour samples with the divers spending about 45 minutes at the deep site. We would come back in into the wet porch, drop off the samples, and sit in our gear for about ten minutes before heading back out. About 5 pm, we still had not seen any strong internal bores, so we decided to change to hourly samples so as not to use up all of our divers allowable dive time.

The 5 pm dive team went out and took a sample in warm low current water. We felt what we thought was a change in the current and decided to hang down deep for a few minutes. Suddenly, we saw a huge wall of cloudy water full of algae - stirred up from the bottom - and the current started racing. The water temperature dropped from 28.8 C to 25.5 C in less than 2 minutes. This is exactly the event we hoped to capture.

As the leading edge of the internal bore passed by, the mixing region between the two water masses had a shimmery unreal quality - picture being able to "see" the water (this is similar to the shimmering waves of heat you can see rising off a road on a sunny day). Yet, ten feet off the bottom, the water was warm and the current was light. We were jumping up and down with excitement on the bottom (well figuratively speaking) and the crew back in the habitat were jumping up and down as well (they could see the temperature signal from a remote sensor that has a display back in the habitat). The things scientists get excited about...

We took some more samples and within ten minutes, we could feel the current dropping and the water warming slightly. This experience was absolutely amazing. After 8 years and hundreds of dives at this site, I had never experienced this phenomena, though we have often seen that it happens from our instrument data. The benefit of spending large amounts of time each day in the water, I guess. So, the long day continues for the other divers, but even if there are no additional bores, we know that we captured at least one major event, and the sampling was a success.

Later that night …

So it's actually Monday, now. About three o'clock in the morning. We just finished an eighteen-hour nutrient sampling bonanza. The grand finale started sometime after midnight with a rapidly-building storm overhead on the surface. We could hear the rain quite clearly and rapid flashes of lightning lit up the ocean in bright blue, casting our shadows upon the bottom. We pulled ourselves down the excursion line to our research area in 105 feet of water, stopping several times to stare up into the darkness, mesmerized by the bursts of lightning flashing overhead. But no thunder. A silent thunderstorm. While we each travel with three separate lights, much of the night diving was spent with our lights turned off. We found the sea to have a remarkable natural light of its own. In spite of the fact that it was a stormy and moonless sky above, we were able to see well enough without lights to navigate and perform much of our work. We easily recognized one another by the glowing bioluminescence that streamed off of us as we moved through the water.