Blender Fluid Baking taking so long I am trying to make a little coastal scene, very basic just the odd wave and clash with a rock or two.

The fluid sim bake is 771mb, why does it take 2-3 hours to bake that?

My computer has these components; 
CPU - Ryzen 5 1600X @ 4.0 GHz
GPU - GeForce GTX 1060 6GB
RAM - 16GB DDR4 @ 2400 MHz

I’ve got the preferences for the CPU and GPU turned on in CUDA.
Nothing else is up on my computer other than Blender.

I have been working in Eevee but I’ve realised to render I’ll have to use Cycles because of a material I have made won’t show up in Eevee.
With a complex, i.e. demanding, fluid sim as it is in your case (the hardware needs to calculate the wave hitting the rocks, turbulences etc as well!) it's best to use both CPU and GPU. Especially if the sim has several hundred frames, which means their number should be reduced. And, apart from the above, try the ca. 200 resolution. It's the max res I used and water didn't look awful.