From the novel "Lord of the Flies", the reason Piggy splashes Ralph with water was that Ralph keep squirting water into Piggy's face, thereby wetting Piggy's glasses. Piggy's retaliation shows that he is becoming more protective of his glasses, which symbolizes his feelings towards maintaining civility on the island. At this point in the novel, Piggy realizes the importance of remaining civil and defending himself against the impending barbarism.