Is it normal to find water under basement concrete?

My house is 21 years old, and I’m currently renovating a bathroom in the basement, located in one corner of the space.

To install PVC pipes for the shower, I had to break through the concrete slab. After removing the slab, I found a layer of styrofoam, a poly vapor barrier, and about 4 inches of gravel underneath. While digging through the gravel, I also discovered a 6-inch drain.

While digging out the gravel, I noticed water beneath it. The water level has remained steady for the past two weeks, even after rainfall. It is approximately 7 inches below the underside of the concrete slab.

Is this normal?