Lower intensity over time on effect

I am very new when it comes to lighting, so bare with me. For an event, I am running a sequence of automated lighting. The idea I envision with the lights is that an "underwater" effect happens (I was able to make this). But as the scene goes deeper, the lights get darker (Less intensity).

I currently have the effect running 5 steps, lighting up certain lights randomly from 10 to 100 intensity. This gives me the desired look, but I am not too sure how to make it fade down in intensity over time.

Envisioned Sequence:

  1. Bright underwater effect (near surface)
  2. Scene is descending (Getting darker)
  3. Reach bottom (Still subtle light, about 20% intensity max on effect)

All of this would happen over about a 14 second period.


How would I do this?

Thank you for any help!

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