Lower the water level to expose the rocks

Jason Yip
2 min readDec 19, 2021


Migrated and modified from my old blog

There’s a metaphor used in Lean circles about seeing inventory as like the water level in a body of water. By lowering the water level, you expose rocks (i.e., problems) that you would otherwise not be able to see and therefore allow you to remove them. NOTE: You need to be careful not to lower the water level too quickly as you may end up just crashing into the rocks rather than removing them.

High water level hides the rocks.
Lowering the water level exposes the rocks.
Now that the rocks are exposed, you can work to remove them. You can now operate at a lower water level.

Time as the “water level” in software development

I’ve used this same metaphor when talking about software development but using time instead of physical inventory to be the water level. Reducing time frames (i.e., shorter timeboxes) helps expose problems that would otherwise not be seen.

Lowering the water level and discovering people who can’t actually swim

A somewhat serious joke is that by lowering the water level, sometimes you notice that people are standing on previously hidden rocks and you realise that they didn’t actually know how to swim. The response is not to denounce them for their inability to swim but rather to help them learn to swim.



Jason Yip

Senior Manager Product Engineering at Grainger. Extreme Programming, Agile, Lean guy. Ex-Spotify, ex-ThoughtWorks, ex-CruiseControl