Continuously dunking my head into and out of water while wrestling a 250 lb inanimate object in 4 to 6 foot seas does not sound like my idea of a good time, but this is exactly what is required when the compass on the Fetch AUV needs to be calibrated.
True north is approximately 5.0 degrees west of magnetic north here in Key Largo out at the Aquarius underwater habitat and two minutes of pitching and rolling the AUV while turning it 720 degrees allows it to orient itself. Two snorkelers, equipped with mask, snorkel and fins (an important item I've forgotten in the past and lived to regret) maneuver the robot back and forth from a horizontal to a completely vertical position in the water while spinning it back and forth along its long axis. While attempting this task, the snorkelers must also maintain a safe distance from the boat, far enough that the delicate parts of the AUV won't bang into the boat, but close enough that the serial cable that's plugged into a lap top on the boat doesn't pull the computer into the ocean below, a delicate balance if I do say so myself.
On top of all of that you have your advisor on the boat "coaching," saying things like "you have to make slow, graceful movements, like a ballet in the water," when all I'm trying to do is keep my head above water and make sure I don't drown on my first day of AUV ops here in the Keys! All in all, it turned out well and only took two exhausting tries to successfully calibrate the compass. A little bit of surface-driving practice and sending Fetch on two practice dives means we're ready to go out tomorrow and get to work on what we really came here for: mapping the habitat!