Thanks everyone.
Looks like I will need to cover them, but want a cheap option.
1. I imagine paint is not cheap for something like this, if it is to last any time..
2. Unless can get cheap wood from somewhere this is usually an expensive option too, although lasts longer.
3. I have seen covers in Lidl sometimes for about €15, but still not that cheap and probably won´t last long.

Any suggestions for cheap, Tarps, Wood, or Paint, please?
Also, how do you know the level of the water when they are all covered up?