This exercise is hard!

Our current homework contains the task of trying to draw fire, water, steam, clouds, etc, without actually drawing them. They are supposed to be the negative space.
This is doing my head in.
I took the camera out when I took Penny for her daily outing, in the hopes of getting some images that may inspire me.
The only ones that seem at all possible are these and I'm not too sure what I will do with them.

Penny got into this one, unfortunately the water is smelly. Now she is too.

I suppose I could go with an old tried and true image, my cliff face one. I'll give it some thought.

I took a couple of cloud pics recently too, will have to try one of these soon. They only have to be little images, 10cm x 10cm, but when you don't draw much, it is daunting.

Suppose I had better go and get the paper and see if I can come up with something. At least I can have the image up on the computer and keep it in front of me, not try to do it from memory.
I certainly can't be bothered printing them out, they are not fabulous pictures and it is too expensive to be printing them out when I don't think this is going to be a very successful activity, but you never know your luck in a big city, they might work out.