1991 ls 400 went through a large puddle and now won't start any ideas as why

 

Probably has something to do with going through the large puddle.

 

How deep was the water and how fast were you driving thru it?

 

The engine could be hydro-locked if you got water in it through the intake. If there's still power, I would take the spark plugs out and then crank the engine to get the water out of the cylinder walls

If you're lucky, that could work. It goes back to the question of how deep was this puddle you went through