Rapboat's Questionable Query

Alright, listen up, you chucklehead. This joke is all about a sneaky, suggestive question. "Rapboat" sounds like "rowboat", right? So, the mom is asking if the boat is docked. But "is it in yet?" also sounds like she is asking about sex, which is a dumb thing to ask your son. And you, my friend, probably have trouble tying your shoes.