I took him shopping at Riot! Carousel for plasticine, different types of clay and other sculpting paraphernalia earlier this year. What he's done was he sculpted a rough idea of what he wanted to make, and fashioned it out of Blu-Tack.....

 

 

Notice the 2 tone? The "underbelly" was made out of newer and cleaner Blu-Tack while the rest of the shark was made out of his dirty piece of Blu-Tack which he kneads with his feet against the floor.

 

First he used the reddish brown plasticine to make the body...

Then he used the red one to make the gums....

The white plasticine for the teeth... it was a very tedious process to make 1 tooth at a time... Sharks apparently has hundreds of teeth...

This was how he did it.... bit by bit, tooth by tooth....

White plasticine for the underbelly....  it's still unfinished at this stage but you get the picture...