How dangerous was it to be a coast watcher during the Pacific War?

The movie, South Pacific featured two "coast watchers" as heroes, the American, Lt. Joseph Cable, and the Frenchman, Emil de Becque, who observed, and reported on Japanese naval movements. The Japanese treated these people as "spies," and killed them at every opportunity. In the movie, Cable died but deBecque survived.

How dangerous was it to be such a coast watcher? Could they camouflage themselves and hide in the vegetation, and mostly survive? Or did "coastwatching" require them to expose themselves, use binoculars and radios, and generally make it obvious to enemy ships and planes as to what they were doing? Did the Japanese land troops to make "sweeps" of areas that coasts watchers used?

Put another way, what were the sources of risk to coastwatchers, and what evasive actions did they take?