My puppy likes the water

My puppy likes the water.
My puppy likes to swim.
I've never seen a puppy
who swims as much as him.

He swims not on the surface,
but only underneath.
And maybe I should warn you,
he has very scary teeth.

Whenever people see him
they're frightened of his grin.
Or maybe it's his lack of fur.
Or maybe it's his fin.

If you should buy a puppy,
just get the kind that barks.
Don't be like me. I bought mine
at a store that just sells sharks.