The monster for this episode would show up again in color the second season in the aptly named "Deadly Creature Below!"
(Following the accident to the test hull, Falk awakens in the decompression chamber. Crane is still unconcious; Falk awakens Archer.)
Falk: I had to do what I did so you could continue your work. You must understand that.
Archer: I understand you perfectly, Falk. You're afraid I'll tell how Tracy died. I won't. If I could bring him back by exposing you, I'd tell--not out of any childish sense of right or wrong. But only for the pleasure of destroying you, Falk.
Nelson: I must confess, Lee, to enable Seaview to get to 36,000 feet, I'd make a deal with the devil himself ..... or Bentley Falk.