Reduces physical damage taken.
Water Shield effects are given two numbers, call them X and Y.
Damage less than or equal to X is received normally.
Damage between X and X+Y causes the unit to take X damage and have the remainer converted to hero healing (like Prayer).
Damage greater than X+Y causes the unit to take X damage, the hero heals for Y, and any further damage is ignored.
Unlike Ice Shield, the Water Shield ability is not bypassed by Infiltrator.