That would be a disaster for sure. One Chinook costs $38.55 million! That's more than a JF-17 Thunder! That's crazy if you think about it in those terms.
JF-17 Thunder:
Unit cost Block 1: US$~25 million Block 2: US$ ~28 million Block 3: US$ ~32 million (planned)
It looks like it can easily sink if the cabin get's overflowed and flooded. The Iranian one looked like the water had filled most of the cabin and the rear cargo door barely had any space for the dinghy to get in!
EDIT: Actually, now that I looked at it again, the Iranian one has the rear cargo ramp up and it doesn't look like any water is in it. Pretty slick.
They probably need to keep the rotors running and create a bit of lift to prevent it from sinking, is my guest. But if you look at some of those pics, some of the rotors are barely spinning. It is risky for sure.