Yes, flying over water is safe, and thousands of pilots do it safely every day. A malfunction, such as an engine failure, won’t compromise the safety of modern airplanes.
There is a very, very low chance that the engines on twin-engine aircraft will fail while flying over water. They have designated backup airports along the flight in case that occurs.
Pneumatic and hydraulic systems, as well as generators, have numerous redundant systems that can safely provide the required service in the event of a system failure.
