The Modern Hebrew word for a crocodile is “taniyn” (Strong’s #8577).
This word is also a “Biblical Hebrew word” and appears twenty-eight times in the Hebrew Bible, including the following verses:
When Pharaoh shall speak unto you, saying, Shew a miracle for you: then thou shalt say unto Aaron, Take thy rod, and cast it before Pharaoh, and it shall become a serpent (taniyn). (Exodus 7:9)
And Moses and Aaron went in unto Pharaoh, and they did so as the LORD had commanded: and Aaron cast down his rod before Pharaoh, and before his servants, and it became a serpent (taniyn). (Exodus 7:10)
Is it possible that “Moses’ staff turned into a “crocodile instead of a serpent”? Yes, I believe so.
The “usual Hebrew word for a serpent” is “nachash” (Strong’s #5175) and this is the word used in these two verses:
And he said, Cast it on the ground. And he cast it on the ground, and it became a serpent (nachash); and Moses fled from before it. (Exodus 4:3)
Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river’s brink against he come; and the rod which was turned to a serpent (nachash) shalt thou take in thine hand. (Exodus 7:15)
According to these verses, Moses’ staff turned into a “taniyn” but it is also called a “nachash”.
I am of the opinion that the Hebrew word “nachash” means “reptile” which could be a “serpent” or a “crocodile”.
This leaves us with the word “taniyn”.
In Genesis 1:21 the “taniyn”, translated as “whale” in the KJV, appears “to live in the water”.
In Psalm 91:13 the “taniyn” translated as “dragon” in the KJV, appears “to live on the land”.
While there are some “serpents” that do “swim in the water”, they are “predominately a land animal”.
The “crocodile” however “is at home in the water and the land”.