The Monster That Challenged the World (1957)

[Xenorama]

Tim Holt ... Lt. Cmdr. John 'Twill' Twillinger
Audrey Dalton ... Gail MacKenzie
Hans Conried ... Dr. Jess Rogers
Harlan Warde ... Lt. Robert 'Clem' Clemens
Max Showalter ... Dr. Tad Johns (as Casey Adams)
Mimi Gibson ... Sandy MacKenzie
Gordon Jones ... Sheriff Josh Peters
Marjorie Stapp ... Connie Blake
Dennis McCarthy ... George Blake (lab assistant)
Barbara Darrow ... Jody Simms
Robert Beneveds ... Seaman Morty Beatty (as Bob Beneveds)
Michael Dugan ... Clarke
Mack Williams ... Capt. Masters
Eileen Harley ... Sally
Jody McCrea ... Seaman Fred Johnson

a pretty shameless rehash of THEM (1953), but quite fun nonetheless.
an undersea earthquake releases an ancient annalid (er, segmented
worm) which immediately starts to both feed on the locals and breed
new critters. how will they ever stop it?

the monster is a full sized mock up, and pretty effective. the deaths
are kind of gruesome, and despite the small child, this might give
kids some good sized frights. some of the acting is only adequate,
but it suffices. the monster does a lot of damage to the lab in the
final fight.