A is for Arachnophobia

An idea and consequent storyboard that could become the opening to my Phobia animation.
It starts out by showing the Swimmer Man in his natural home, swimming, happy until a shark's fin appears and he swims to an island where the shark can't reach him.
The island is covered in sharp black rocks which SM walks through slowly as little spiders creep about hidden from his view, but not ours, the shark meanwhile goes away bored... (or he can burst out and scare SM into knocking into a rock).
He looks round one rock and comes face to face with a little spider, he steps back startled and knocks into a rock where lots of spiders crawl all over him making him dance about trying to get rid of them... he eventually gets rid of all of them and dives into the water again.

I sketched out a rock-crab/spider thing that could wake up after he's gone or maybe make it more spider like and less like a shell of a crab though if I'm to use it.