This was a great show. First of all it had Bill Katt (who should've been Luke Skywalker instead of Mark Hammill, because Bill Katt can, you know, ACT), it had Connie Sellecca, who was an early crush (of course before I found my true love Jane Badler). I remember that the alien eel thing scared the crap out of me, despite that they were obviously filming in such a way as to protect their budget. (Re-watching the nuclear attack scene in the 1980s made-for-TV The Day After similarly reactivated an old fight-or-flight response.)
Watching it again as an adult in comparison with modern "rules" for television genres, I found it interesting that the astronauts on the space shuttle unambiguously died. Today, that would be allowed in a serious prime-time show, but not a show with tongue-in-cheek overtones like this one had. I also liked that a random FBI agent comes into a California dam facility and demands an immediate water release so that a reservoir can be filled, and the guy listens to him! Of course we were much more loosey goosey in this state back before California turned into Arrakis; today the alien eel would have overrun the state!