(water) is waist deep

To explain how deep some water is in a pool, ocean, lake, etc., English speakers sometimes explain what part of their body the water reached to. To do this, they use the expression "___ deep":

Don't be scared. It's only waist deep.

Aside from "waist deep", we also use the expressions:

ankle deep

knee deep

chest deep

neck deep

This phrase appears in these lessons: