I vividly remember seeing that movie with my father as a 12-year-old. The crowd outside the theater was enormous and my father fought his way to the ticket booth, dragging me with him. It was a PG-13 movie at the time and anybody younger had to have an adult with them. People who couldn’t get in waited the 2 hours outside for the next showing. It was insane, the box office that movie did that summer.
If it was the first run it could not have been a PG-13. Jaws came out in 1975 and the first PG-13 rating was Indiana Jones and the Temple of Doom in 1984.