It should be possible to have the pistons reconditioned.
If the cylinder liner lubrication was destroyed by the water ingress, causing the excessive wear to the pistons, there will probably be excessive wear to the cylinder liner as well.
If there has been scuffing damage to the contact surfaces you may have to have the liners honed or replaced as well as the pistons re conditioned.
If there is damage to the liner, that could damage the new /reconditioned pistons.
I would suggest that you ask Wartsila to send a service engineer to inspect the damage and advise on remedial action.
I presume that the engine is still running, and you could probably continue to run it for some time. However, damage to the pistons and liners will cause blow past and loss of power. The wear on both the piston and liner will accelerate and could put the piston beyond repair.
It is always better to ask a stupid question than to do a stupid thing.