The scuba instructor said that there occasional nurse checked my swim near the reef, but it’s not aggressive species seeing a shark was improbable, but he said not to panic if we do what does the term improbable mean? In the context

Unlikely
Difficult
Harmless
Unpredictable

In the given context, the term "improbable" means unlikely.

In the context provided, the term "improbable" means "unlikely."