Translation:The spell is going to cause him to cry when he sees water.
Can הולך really be used like this as a future tense? I've never seen that before.
It's colloquial but very common. It is more correct to use עומד ל for this purpose, but we burrowed הולך ל from English.
Its a common phenomenon in many languages that the verb "to go/walk" will become grammaticalized. Its not a specific borrowing from English into Hebrew. It's a general language trend. Same with עומד להיות and הולך לעשות.