How can I calculate the ground reaction of a grounded ship？?

‘reaction’? What do you mean? When it tips? If the hull tears?

The ship is going to list based on weight distribution and outside forces like wind and waves hitting it. The shape of the hull, of course…... This isn’t a good question. Are you writing a book or something? I don’t understand why it is such a poor question or why you would need to ‘calculate’ such a thing. What sort of ship are you even talking about? Are you an insurance adjuster or a ships captain? *shutters at the thought.

I’m starting to imagine that you are a high seas pirate looking to ground a ship.

*shudders

Take the weight of the ship, then subtract the buoyancy force of the displaced water.