i drove my car through a puddle of water and it shakes real bad. I had a mechanic check the spark plug and wires he told me there is no pressure on plug one. He also checked the sensor behind it and still nothing. Basically he is saying I need a new engine. Is this true?

 

How deep was the water? It sounds like he is saying you hydro locked your engine(when the intake sucks up water and it gets into the cylinders, water can't be compressed like air so it does in fact destroy an engine). But you'd have to drive through some pretty deep water for this to happen

 

I was going to say hydrolock as well.

In your case I would have a cylinder leakdown test performed; said test will help determine whether the engine failed in the lower end or the top end. If only the top end failed, you can swap the head and be good to go, however, if the lower end failed, it's time for a new motor.

 

​​​​​​​how much would that cost?

 

How much should what cost? The cylinder leakdown test or a new motor?

 

For an added test it really shouldn't cost much if anything - guess ~$30. Or better yet, ask this question.

"Are you telling me the valves are bent or is there damage to the lower end of the engine"