YOU SAID:
she buys seashells down by the seashore
INTO JAPANESE
彼女は海岸のそばで貝殻を買い取る
BACK INTO ENGLISH
She buys seashells by the shore.
INTO JAPANESE
彼女は海岸のそばで貝殻を買う。
BACK INTO ENGLISH
She buys seashells by the shore.
That didn't even make that much sense in English.