Heartbeat Boat — Why do rowers need a drummer?

Why does a rowing crew need someone beating a drum? Because eight people can only pull as one if they already know exactly when the next stroke is coming — so they start their pull before the drum even lands. A steady beat is a promise they can lean on, and a steady drummer beats a fast one every time. Take the mallets yourself: wreck the stroke, watch eight rowers turn round and glare at you, then find the pulse that puts all eight oars in the water at the same instant.