Bomb Defusing quests require you to disarm some bombs, preferably without getting seen. However, the mission will continue if you’re detected, but the enemies will arm the bombs and a countdown will appear at the top of the screen. Should the countdown reach zero before you can disarm the bombs, then you will fail the mission.
There’s a total of seven Bomb Defusing quests in the game. Completing five and all seven will reward you with Rupees bonuses, while completing two will unlock the Bull signature weapon in the shop. Also, completing three of them will net you the Defuser achievement/trophy .