We Keep Looking at the Sky, but They Might Be in the Ocean

I was recently thinking about other forms of life, and about how governments have been increasingly putting this idea out there lately and no longer outright denying their existence on Earth or the possibility that they may have been influencing humanity for thousands of years.

That got me wondering: how could they remain unnoticed by us? Where could such a large population possibly hide?

I came to the conclusion that they most likely live in the depths of the ocean, and that would explain a lot. For example, if you live in the ocean and trigger a global flood, it wipes everything out for us, but it does nothing to them, because they are already in the water. They could move around underwater without being noticed, live there unseen, and so on.