I needed some time to just learn from the Blender default settings instead of watching hours for hours bad tutorials.
So just do this:
Create a cube. Objects -> Quick effects -> quick liquid. Then just check the "mesh" box in domain settings.
If you just run the simulation in material preview you will get:
And this is "only" a resolution of 32!!
And in my opinion it looks already great.
If you then check the material Blender gifted us:
That's pretty basic and looks already awesome.
Then you should play around with settings and tweak some settings.
Checking "diffusion" will make some more splashes:
Increase resolution in water simulations is always a good idea. But yes, it will take machine power and your time.
From left to right:
Resolution 32, 32 + diffusion, 64, 128
If you want "detail" explanation why yours doesn't look realistic, please provide blend file so we can check it out. It depends not only on domain settings, but on shader, inflow and light settings as well. And for water simulations in 99% of all cases Cycles will do a much better job than EEVEE. I my examples here are just EEVEE....
Another hint (no, unfortunately i don't get any money from them - not even just a cup of coffee): Flip Fluids is a great add-on which makes fluid simulations not only look better but even quicker and easier to use. Yes, you have to pay for it but i never regret buying it. And it has e.g. inbuild materials for different fluids.