The M-drop is a defensive scheme in the sport of water polo which is mainly used when the offensive team has a strong center or the center defender has lost position.
The sixth offensive player, known as the "center" or "set" plays in front of the goal.
From left to right, and moving around the circle, the offensive players are named 1, 2, 3, 4, 5, and the set is 6.
Center defenders attempt to "front" the offensive player by working for position and placing their body between the center and the rest of the offense.
They also split in between the set and their player, hence the name M-drop, from the ‘M’ shape created.