Scene with Eevee in blender.

The first thing I did was create an Icosphere to which I added the following modifiers:

-Bevel. 

-Decimate.

With this we obtain the crystal of the scene which we will duplicate and place to our liking.

I continued creating a cylinder and little by little I shaped it until I got a "Cave" shape.

Once that was achieved I gave it a cave texture as follows:

Once the cave is finished, we go to the water, it's even easier than the cave, since I created a blueprint and put it on the floor of the cave.

Once I got it done, I gave it a water texture as follows:

When I have solved the cave and the water, the next step I have done is to put "stars" around the cave to give it a touch of light and fantasy.

I have created an Icosphere which I have linked to the cylinder that acts as a cave in the following way:

As last details I put the crystals in the center of the cave and the water.

To finish I put a couple of lights a few last touches and that's how the final result was.

I hope you liked it and that it serves you.