Unfortunately, I don’t have much in terms of details to provide for this but here goes. Hopefully someone will remember this and the years of torture I’ve had trying to remember the name will be over!

Timeframe: early 1980s

TV/Movie: I saw it on tv though I don’t know if it was a tv show episode or a tv movie. My gut says it was a movie, possibly even one of Disney’s early entries into the scary genre…but I’m not sure.

Bits of movie I remember: There were kids, a beach scene, a tunnel or a sewer that they climbed down into with flashlights. They found the bones of a girl in the tunnel who had gone missing years before. And I think there was a van parked by a grassy beach.
(I know what you’re thinking: a bunch of kids…tunnels…bones…she must be thinking of Chester Copperpot’s skeletal remains in The Goonies. But I assure you,  this was not The Goonies)

Like I said, not much to go on but if anyone can help, I’d appreciate it immensely. Thanks!