"What on earth did he do... That's right! The dining car!"
Since it was the dining car of a luxury train, the bar would surely have effervescence agents for making carbonated drinks. If those were scattered on the floor of the compartment, they would generate a lot of foam when touching water, preventing the Water Demons from entering those compartments unless they were cleaned, at least for a short while.
"Forget it, I never thought it would be easy to achieve the goal anyway. Let's stick to the original plan and try to deplete the young master's stamina while maintaining our own combat strength. With prey like this, give him a chance to catch his breath, and the whole operation is screwed."
His right hand made a snapping sound, and a group of grey shadows emerged outside the windows, writhed a few times, then swam towards the rear of the train.
