"Explorers", produced by Spielberg, special FX by ILM. If you want to read the Cinefex article on the film, go to the Cinefex site and search for the online article. Same team eventually went on to produce "Batteries Not Included". I have the ILM effects book describing the making of the movie if you are interested.

If any of you have an interest in any particular special effects film, I have Cinefex mags dating back (patchily) to 1988. Ask for them at the Amersfoort meet.