Now they all down at the beach washing off the fish
Was Blackbeard til I brought the Roc into your ships
“Blackbeard” probably refers to music pirates and those who leak his music (see Lupe’s OkayPlayer interview).
Lupe brought the “rock” into your ship — i.e.:
He sank your enterprise with a well-placed cannonball, like Blackbeard the pirate.
He caused you to run aground, like the huge rock on which the Exxon Valdez ran aground, spilling oil everywhere. This is meant to recall the image of oil-soaked fish in the previous line.
He attacked your team like the mythical Roc, a giant bird of Arabian legend, which attacked the fleet of Sinbad.
He brought the full force of Roc(-a-fella) to bear on your weak team by enlisting Jay-Z to Executive Produce his album and guest on this track.
To help improve the meaning of these lyrics, visit “Pressure” by Lupe Fiasco (Ft. Jay Z) Lyrics and leave a comment on the lyrics box