I think you just have to read body language.
If you put a snake in a tub of water and it starts whipping around, then obviously it "hates" where it is and it's freaking out!
Now on the other hand if you have say a garter snake (or one that eats fish. If you place your feeder fish in the tub (Providing no way for THEM to escape) and something for your snake to hang off of, it might provide YOU with some entertainment and the snake with some major hunting time.
Example: my blood python
At the store when I first got him out he was fine, tounge flickering, breathing normal..etc...etc..
all of a sudden he stuck his tounge out, curled it up (towards his nose), and puffed up as big as possible! He brought his tounge back in, deflated himself, and started all over! I took this as a "warning" sign that he wanted to be put down.
Now I have NEVER seen a snake do this. And I only ASSUMED that he was angry, and about rady to strike, or something severly wrong with him. Considering that he was JUST FINE, like 2 seconds before hand, I took it he was fairly upset and wanted to just be left alone.
If your really good with your snakes, or have been with particuler snakes for a while, you might even be able to get "vibes" off of them on what their "mood" is like.
I would love to hear what others think!
Neptune, Zion, Enigma,