Two weeks at the bottom of the sea.
As part of astronaut training we lived in Aquarius, 60 feet down, off the Florida Keys. We simulated Mars ops with a 30-minute time lag on all communications, so we sent videos to mission control.
A great place to simulate Moon/Mars gravity for spacewalks, using weights and water buoyancy. Also for learning the forced, beautiful isolation of life on a space station.
(featuring Dr. Steve Chappel and
@astromarshburn)