Question

insert dashes where needed.

the competitive diver jumped from the bridge an impressive limestone structure suspended nearly eighty feet above a deep gorge while television cameras recorded the amazing feat.

Explanation:

Dashes are used here to set off a non-restrictive appositive phrase that adds extra descriptive information about the bridge, separating it from the main sentence to improve clarity.

Answer:

The competitive diver jumped from the bridge—an impressive limestone structure suspended nearly eighty feet above a deep gorge—while television cameras recorded the amazing feat.