The double-pause slide exercise.
Lots of coaches use “single strokes” or “pause paddling” exercises to teach the crew how to arrive simultaneously at one point in the stroke cycle.
When done really skillfully, it’s a picture of symmetry.
Here are the Australian womens eight doing a double pause – twice up the slide (approx 1/4 and 3/4 slide) with one full stroke in between.
It really shows up the small inaccuracies – look closely at bow side. See the 3 girl is late on the catch and the bow girl early in the first couple of repetitions. Also 3 seems to get caught in at the finish – she holds the blade under the water just a fraction longer than she accelerates it.