I got a lab making lycanthropes in my game, which my players are currently trapped in. There are two days to the full moon, and they have a three day window to escape. I wanted to make one of their fellow prisoners a werecroc, and the stats I have in mind are basically giant crocodile stats, with a few changes:

18 strength, and normal intelligence/wisdom (10 or so) and lower charisma.
Less damage on the bite/grapple: 15 (2d10+4)
The regular immunities of a werecreature, along with the Hold Breath
think that would make an appropriate challenge for a level 4 party?