Is it possible to use one mask to cut into a different mask?

I am using the select sky mask. Then using a duplicate of this and inverting it to select everything instead of the sky - called mask 2.

What I now what to do is use a brush mask of water already created to cut into this to create a new mask that is everything except sky and water. (rather like it is possible to do in Illustrator)

Is it possible? or do I have to subtract from the mask and manually mask it with the brush?