What a beautiful morning, even at 50 feet. I glanced out the porthole as I stumbled from the bunk room – the visibility, which can be quite variable, looked pretty good today. That always helps to lift my groggy spirits. Climbing into a damp wetsuit isn’t always the most pleasant early morning experience, so knowing that the conditions are good is encouraging. As Sal and I glided out toward our 105 foot deep work site, we looked up to see a calm day 60 feet above us. The largest waves were those that came from our bubbles as they broke the surface. A mooring line we passed hung in the shape of a “U” – no wind or current to stretch out the line. The dark outline of birds could be seen soaring way overhead.

“Ah yes.” I thought, “Why doesn’t everyone do this for a living?” Our arrival at 105 feet told me why – COLD water!!!

Sure enough, the phenomenon that we are here to study was surrounding us with some of the coldest water we have felt so far this trip. This is one way to clear the morning cobwebs from the head, but not one I necessarily recommend. Even in a 7 mm wetsuit, the chill quickly penetrates to the bones. Within 20 minutes, we were happy to be headed back to the habitat with some samples we had collected. The warmth was fleeting though, because soon we were back down at depth to collect water samples and continue our day’s work. The interesting thing about this morning’s cold water pulse was that it was a very thin layer. Immediately on the bottom, the water was cold. Six feet (2 m) above the bottom, the water was about 6-8 degrees F (4-5 degrees C) warmer. Of course we take advantage of this: work for a while on the bottom, then pop into the warmer water to stop shivering, then back down to the bottom to work. At times we could have one hand on the bottom in cold water and the other hand up a little in warm water – it’s a very distinct boundary. But like I said, this is what we are here to study, so it is a good thing. By the afternoon dives, the visibility had dropped substantially and the cold water had mostly receded.

Much of today was spent finishing up experiments, filling in holes in our data, and starting to retrieve instruments we have placed around the reef. Today is our last full dive day, and it is time to start wrapping up this phase of the work. It never ceases to amaze me how after months of planning, the mission can be over so soon. We keep asking the habitat technicians if they can delay the decompression so we can work for just a few more days, but they just look at us with strange expressions and shake their heads. We’ve thought of holding a coup, but we realized that they are the only ones who know where our air is coming from. Tomorrow begins our 16.5 hours of decompression. It will be nice to see the sky and (hopefully!) the sun on Wednesday morning when we emerge, but our thoughts will always return to Aquarius and to the incredible experience it and the surrounding reef have provided us.