Blood in the Water (Red)

Blood in the Water triggers when it resolves and becomes a defending card on the combat chain. This is an optional effect: You choose whether to either discard a card from your hand, destroy the top card of your deck, or do neither at the time the triggered effect resolves. If you either discard a card or destroy the top card of your deck this way and that card has watery grave, Blood in the Water gets +2.

Destroying the top card of your deck will not trigger any “when this is destroyed,…” effects unless it is specified by the ability’s triggering condition.

Destroying the top card of your deck will not satisfy any condition nor trigger any effects that look at whether you’ve destroyed an object you control (e.g. Merciful Retribution, Ratchet Up) as you do not control the cards in your deck.

Unless a rule or effect allows you to do so, you cannot play or activate defense reactions against attacks where the attack-target is an ally you control.