depend, deep end, deepened

Depend or depend means to rely or trust in--
A pet must depend on you for all of its needs.
You can't depend on the local trains when the weather is bad.

Depend may also mean to be contingent upon--
Salary will depend on level of experience.
Grades will depend on test scores and class participation.

Deep end or deep end ( two words ) means the side of a pool where the water is deepest--where the bottom is farthest from the surface, as opposed to the shallow end--
They won't let you in the deep end of the pool if you can't swim.
The diving board is over the deep end of the pool.

Deepened or deepened is the past tense ( yesterday, or some time ago ) of "deepen", meaning to become or make more deep, or farther from the surface, front, or top--
The puddle in the back yard deepened with the rain.
The snow deepened overnight.

Deepened is also the past tense of "deepen", meaning to become more intense, as color, weather, or darkness, or figuratively, grief or sadness--
The shadows deepened as the night wore on.
His sorrow deepened with the passing years.

Now that you know that, you can say--
"We depend on the lifeguard to watch the deep end of the pond, where the water has been deepened by dredging."

Note -- "depend" is a verb ( action word ), with a form for first, second, and third person, singular and plural, past, present, and future--
I depend, you depend, he depends, we depend.
I am depending; you are depending. We are all depending.
I depended on it. You depended on it. he depended on it. We depended on it.
I will depend on it.