scratch the surface (?.)

• be innocent of
• coquet with
• dabble
• give up
• have no idea
• know a little
• know not
• know not what
• know nothing of
• not know
• not rightly know
• pass
• skim
• skim over
• skim the surface
• smatter
• touch upon
• toy with
• wonder
• wonder whether
• wot not of