  Sensor networks provide services to a broad range of applications ranging
from intelligence service surveillance to weather forecasting. Most of the
sensor networks are terrestrial, however much of our planet is covered by water
and Underwater Sensor Networks (USN) are an emerging research area. One of the
unavoidable increasing challenge for modern technology is tolerating faults -
accepting that hardware is imperfect and cope with it. Fault tolerance may have
more impact underwater than in terrestrial environment as terrestrial
environment is more forgiving, reaching the malfunctioning devices for
replacement underwater is harder and may be more costly. Current paper is the
first to investigate fault tolerance, particularly cross layer fault tolerance,
in USN-s.
