That's just scratching the surface like Triple Axels

from Lupe Fiasco – Audubon Ballroom Lyrics on Rap Genius

Correlating with the Titanic metaphor from the previous line, when the Titanic hit an iceberg, it scratched the surface of the ship, and figure skating is, indeed, scratching ice.

On a deeper note, a Triple Axel is a jump performed in figure skating. Upon landing, the blade from the bottom of an ice skate scrapes up a little ice from the top of the surface of the ice rink. Hence, you just “scratch the surface”, like when you do a triple axel.

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