This idiom or expression (which is not polite) means:

In trouble.
Under pressure.
In a messy situation that’s not easy to get out of.

A. Have you seen the test results?
B. Yes, I know, we’re deep sh-t!!

Also see:
In hot water.

This idiom or expression means:

Under (a lot of) pressure.

We are under the gun to get the play on the road by next week.

This idiom or expression means:

In trouble.
Under pressure.

Political scandals have landed several public figures in hot water.

Also see:
In deep sh-t. (Not a polite thing to say.)

This idiom or expression has to do with:

Changing one’s position or decision under pressure.

This idiom or expression is about:

Having lots of responsibilities.
Being under extreme pressure.

Faced with a number of large scale problems, the president is finding himself in the hot seat.

This idiom or expression means:

Putting someone under pressure.
Forcing, or trying to force, someone to do something.

A. He’s not coming to my wedding.
B. I know him. You’ll have to hold his feet to the fire before he changes his mind.

Also:
Put someone’s feet to the fire.
Keep someone’s feet to the fire.