YOU SAID:
Narwhals, narwhals, swimming in the ocean.
INTO JAPANESE
イッカクは、イッカクは、海で泳ぎます。
BACK INTO ENGLISH
Narwhal is, narwhal, you swim in the sea.
INTO JAPANESE
イッカクは、イッカクである、あなたは海で泳ぎます。
BACK INTO ENGLISH
Narwhal is a narwhal, you can swim in the sea.
INTO JAPANESE
イッカクはイッカクである、あなたは海で泳ぐことができます。
BACK INTO ENGLISH
Narwhal is a narwhal, you can swim in the sea.
That didn't even make that much sense in English.