YOU SAID:
Sally sells seashells by the seashore.
INTO JAPANESE
サリーは、海辺で貝殻を売っています。
BACK INTO ENGLISH
Sally sells seashells by the sea.
INTO JAPANESE
サリーは、海で貝殻を売る。
BACK INTO ENGLISH
Sally sells seashells by the sea.
That didn't even make that much sense in English.