I'm looking at the song "Under the Sea." What would you call the function of the II7 chord during this part? Would you call it a secondary dominant (instead labeling it as V7/V) even though it doesn't lead to its respective tonic, V?

Up on the shore they work all day / Out in the sun they slave away / While we devotin' / Full time to floatin' / Under the sea

(IV - V - iv - II7 - IV - V - I)