Two divers measure coral near Aquarius.

Underwater "Spacewalking"

The NEEMO experience parallels space flight in several ways. Like a spacewalk, a dive is planned in advance with a series of objectives in mind and a timeline for reaching each goal. Also like a spacewalk, the duration of each dive is limited by the consumables available to the participants outside their safe havens. Participants often mention the analog of deep-sea diving to spacewalking.

During NEEMO 3, Astronaut Danny Olivas wrote: "Regardless of how tired and hungry I get, I regret having to come back to the Hab. It's one of those things that you just know you're gonna miss the next amazing thing, waiting right around the corner, if you go in now. If only you had just a few more minutes ... just a few more seconds. My appreciation for safety (and air) always overrides, however, and in I go. I imagine that spacewalking will be similar. To be outside the space station ... looking back at earth ... not wanting the moment to end, but knowing that consumables drive everyone back."

Map of Conch Reef, where Aquarius is located. Numbered areas: 1) Shallow S4 Current Meter; 2) Pinnacle Wall; 3) Deep S4 Current Meter; 4) Northeast Waystation; 5) Ridge Site.

Here is a list of common NEEMO dives and objectives:

Pinnacle Orientation Dive
Aquanaut team visits the south site, beginning at the Pinnacle and transiting toward the habitat. They pay attention to all surroundings and become familiar with topography and excursions lines.

Northeast Site Orientation Dive
Aquanaut team visits the north site, beginning at the Deep transect and transit toward the habitat.

S4 and 5 Leg Site Orientation Dive
Aquanaut team visits the deep site beginning at the end of the S4 line by performing a very large circle sweep.

Site Tagging Task
The Aquanaut team will deploy NASA tags along the excursion lines that will systematically identify the location. These tags will eventually become the basis for an entire grid network of the Aquarius site and are used in conjunction with the Communication Task.

Communication Task
Aquanauts test the power and clarity of the underwater communications system by venturing away from the habitat, measuring their distance traveled and provide comm voice tests at given intervals. The aquanaut buddy pairs transit to many areas on a certain site and provide voice checks, which are documented and used to characterize the useful range of the communications system.

Construction Task
This exercise is completed during five separate dives. During the first exercise, the aquanauts work as a team to locate and transport pieces of the Waterlab and the required tools, which are located in another area. They construct the base unit of the structure, which is in the form of a stack built of PVC. For the second dive, the buddy pair constructs the truss part. During the third dive, the buddy team constructs the antenna and connects cables. The fourth dive includes construction of the solar array and cable connections. During the final dive, the crew takes down the Waterlab.

NEEMO 4 Aquanaut Rex Walheim wrote in his journal: "The task on our first dive was to build a structure called water lab. It was similar to a spacewalk task, but the local conditions add a few challenges that I didn't have to deal with in space. First of all, the current kept trying to separate us from the structure. Then we had a bit of sand get in our bag of bolts. It makes you appreciate the cleanliness of space. We managed to get the structure put together nicely, and then a large barracuda swam into it as if to inspect it. Apparently he approved of our construction job, because he moved on his way."

Coral Science
Aquanauts perform tasks associated with data collection on the coral reef. This involves setting up of transect lines perpendicular to the excursion lines and measuring the size and health of the coral. Each coral is photo-documented and the results compiled and given to NOAA.

Greg Chamitoff wrote in his journal that he enjoyed exploring the reef and gathering data: "Diving today was awesome! We mainly explored the full extent of the major excursion lines. We recorded the depth and surrounding flora and fauna at certain intervals along the excursion lines. We filled tanks at the distant way-stations, and we performed exploratory excursions off of the main lines using our own line reels."

Night Dive
The aquanauts dive at night to experience different techniques, departing the habitat during sunset and diving during nighttime conditions, using specialized techniques and equipment.

Dawn Dive
The aquanauts dive during sunrise to experience changing environmental conditions, departing the habitat 30 minutes before sunrise and witnessing changing conditions.

Aquanaut Mike Gernhardt wrote about terminator diving in his journal: "This morning we made a terminator dive. Something I used to do when I worked in the Islands years ago. We entered the water at nighttime and watched the earth move from night through the terminator into daylight, from the underwater perspective. It takes about 90 minutes to 2 hrs to see the full transformation."