A nonsense riddle asking how many strawberries grow in the sea, answered with an equally impossible number of herrings in the wood. It is the kind of daft logic that lands best once a child is old enough to catch the joke.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
The man in the wilderness
Asked me
How many strawberries
Grew in the sea.
I answered him
As I thought good,
As many as red herrings
Grew in the wood.
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition