After what seemed like a brief two-hour morning dive (this is still about twice the allowable time we'd get on a normal scuba dive) to retrieve our equipment and wrap-up loose ends, we have begun our sixteen-hour decompression - a long, slow ascent that will safely return us to the surface after nine days underwater. Decompression includes breathing pure oxygen, drinking lots of fluids to stay well hydrated, and ascent rates that are as slow as one foot every 34 minutes. It is a period to organize notes, think about some of the amazing dives we've done, and in odd ways remember that for all the technology we have employed we still can only visit rather than live in the ocean.

During decompression Aquarius does not itself return to the surface. Instead, the pressure inside is gradually reduced. Although the pressure changes so gradually that it is not really noticeable, there are some interesting changes. For example: the sink drains, that work based on simple pressure differences between Aquarius and the holding tanks, slow down and finally stop draining as the pressure inside the underwater laboratory drops. We still peer out the view ports and see large barracuda and other fish cruising by, but now that we are locked in, with the hatches secured, there's more of a sense of being separated from the fish and reef creatures. We are leaving their world. Earlier, we could swim out to the reef easily and quickly by getting our gear on, then dropping out the floor of the wet porch into the water.

Our next "dive" will be to the surface.

Once we reach surface atmospheric pressure in the morning, we will move into the entrance lock of Aquarius and close the hatch to the main lock. One of our Aquarius technicians will then drop the pressure back down to ambient (about 2.5 atmosphere at 47-49 feet) so we can exit into the wet porch. We'll make a normal ascent with small scuba "bail-out bottles" to a boat waiting on the surface.

We are pleased that the science has gone so well on this mission. We have a lot of really interesting data to interpret that will hopefully lead to new understandings about internal waves and cold water pulses that deliver nutrients and particles to the organisms living on the reef. In addition to the temperature data and water samples collected for this ongoing study, the long hours underwater have inspired many new ideas for refining and expanding our research.