Possible Clues:

• Of mud, for example, too deep for ordinary shoes
• Like kiddie-pool water, often
• Like the water in inflatable kiddie pools, typically
• Stream measurement
• Wading, perhaps
• Like water in the basement, after some leaks
• Under 6' in depth but standing over a foot
• Nowhere near in over one's head?
• More than a little involved
• (E.g. in mud) over one's shoes