JSC2011-E-016231 (9 Feb. 2011) --- NASA astronauts Chris Ferguson (left), STS-135 commander; and Doug Hurley, pilot, attired in training versions of their shuttle launch and entry suits, are pictured during a water survival training session in the Neutral Buoyancy Laboratory (NBL) near NASA's Johnson Space Center. STS-135 is planned to be the final mission of the space shuttle program. Photo credit: NASA or National Aeronautics and Space Administration