If you want to see the SQL sent directly to the database , you'll have to use some kind of jdbc driver proxy like P6Spy (or log4jdbc).
Alternatively you can enable logging of the following categories:
log4j.logger.org.hibernate.SQL=DEBUG
log4j.logger.org.hibernate.type=TRACE
The first is equivalent to hibernate.show_sql=true, the second prints the bound parameters among other things.