Re: Alfa 156, hydrolock
916 is absolutely bang on the money. Start with the simple things, like charge the battery and see if it turns over (plugs out), after making sure the timing belt is intact. If it is already badly damaged internally this will not make it any worse, and even though he suspects a hydrolock, he's not sure, and it may only be drowned electrics. If thta goes ok, try it plugs back in.
Only if that fails, or if you get nasty noises from the motor do you assume there is worse damage. It'd be nice if someone had a scope to poke down a the plug holes to see if there is valve damage. The main risk with a real hydrolock is bent con rods and a damaged crank.
A drowned engine can easily be a legitimate insurance claim, and I would immediately notify your insurance company immediately of the circumstances, and the possibility of a claim being made. As ever, dismantling is your responsibility, but as soon as you (or garage) find serious damage caused by water ingress, they must stop work to allow insurance co the chance to send an assessor if they wish to do so, and not commence repair work until authorised.