Final answer:
The Oarfish is the cryptid believed to be some form of sea serpent.
Step-by-step explanation:
The cryptid believed to be some form of sea serpent is the Oarfish. The Oarfish is a monstrously-long fish that has been thought to be the inspiration for stories of sea serpents. It has an unusual physiology and is often referred to as a real-life "sea monster."
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