This was a personal project while learning Illustrator. 

(below) final version.​​​​​​​ For the shadow, I just duplicated the whale, decreased the opacity, and added a gaussian blur. I also decided to give it more of a green hue than previous.

(below) shows my decision to simplify the original illustrations that are below these

(below) The image on the (left) is the my original idea for this illustration. I began with the idea that this whale would have its back sticking out of the water. 

I later decided against that.

(below) The lines on the (right) were used to cut the circle on the (left). 

Both were applied as clipping masks, which you can see on my final version up top.