I went fishing in Toledo Bend a few days after seeing it. I was about six. Was scared a shark was going to swallow the whole boat.
I was about the same age... living in Florida. Hell, I was terrified to swim in our own pool in the back yard from thinking that Jaws was such a bad arse shark, he could bulldoze his way underground the few blocks from the ocean to our house and get me in the pool.
The imagination of a 6 year old can do serious damage to itself with just a little bit of encouragement.