Cycles render showing up black I am very new to blender (2.81) and have been following a number of different tutorials to produce this file. 

Rendered images (cycles) were working fine but suddenly they now come up as black screens. I don’t understand as the rendered viewport view shows everything correctly!

I found a forum help post that gave a long list of things to try and fix this issues and I have attempted tthose I understood but none have worked. 

Blend file:
https://drive.google.com/drive/folders/13KHVJxB5VuuFE3hBDRyNraVbIl0MOxwn

If any of you kind folk could take a look and tell me what stupid mistake I have made I would be eternally grateful
There is one large object blocking your view.  

In outliner go to MEGACUBE > POOL > Cube.001 and disable the Render Toggle.
You also see the object in viewport if you toggle the Eye icon.