What is the immediate action if a grenade is thrown at you?

The immediate action when a grenade is thrown at you is to shout "GRENADE!" and hit the deck. This response is critical for several reasons. First, shouting "GRENADE!" alerts everyone nearby to the danger, allowing others to take necessary protective actions. Second, hitting the deck, or dropping to the ground, minimizes your exposure to the blast and shrapnel by providing a lower profile and using the ground for protection. This method is essential because it decreases your chances of being injured from the explosion.

While running away might seem instinctive, it could potentially put you in a position where you are more vulnerable or not able to take cover in time. Simply shouting “FIRE!” does not specifically communicate the nature of the threat, and taking cover alone might not be sufficient if you haven't informed others of the grenade's presence. Throwing it back is only advisable if you are certain you have enough time and distance, which is rarely the case in such sudden and chaotic situations. Therefore, the most effective and safe response is to alert others and take cover by hitting the deck.