You're misreading. If a monster says "When this card is flipped face up" it counts as a flip-effect. If it said FLIP: At the start, then the Water monsters gaining 200 attack would be dependent on the flip. It is not. The ATK gain is not flip-activated, the bounce is. If it had said "When this card is flip summoned," like it does for Swarm of Locusts, then you would be right.