The actors star in the true story of a family struggling for survival during the tsunami that hit Thailand in 2004.
The trailer features McGregor and Watts dealing with the aftermath of the massive flooding in the wake of the disaster.
The film marks Bayona's English-language debut. He is best known for his 2007 thriller The Orphanage.
The Impossible is currently set for a January, 2013 release in the UK.
McGregor recently starred in Salmon Fishing in the Yemen opposite Emily Blunt.
Watts is to play Princess Diana in upcoming biopic Caught in Flight.