Rachael refers to the frivalrous dewgong swimming around the ocean waters yielding a fascination for hispanic guys, yet is oblivious of man's capabilities of using boats to run over their bodies or harpoons to obtain hides; usually eccentric souls who sing really high pitched and will take an eternity to prevent from talking nonsense.
John, on the other hand, refers to the polite, ethical 'white boy' that every conservative parent yearns their daughter to date; he will criticize in every way possible spurting out your flaws and will persist in doing so; sometimes is oblivious to the fun of drinking and marijuana, but hey you can't convince everyone.
and there you have it: opposites
Rachael: *jumping up and down- "yay! hey john! have you heard of the B-52's?!!?"
John: "no, Racheal, in fact im not even highly interested in the sort-"
*puts on record
Rachael: *singing: "Woooh! You're living in your own Private Idaho..."
John: *sighs, "see, i knew we never should've let Jimmy Carter take the presidency